NOVELTY - A polyimide precursor comprises a repeating unit (I) and a repeating unit (II), and is obtained by thermal imidization. The content of repeating unit (II) is 30-90 mol% with respect to total content of all the repeating units. 50 mol% or more of total content of bivalent group produced by removing amino group from diamine in repeating units (I) and (II) is a bivalent group (III) and/or (IV).    USE - Polyimide precursor is used for varnish for forming polyimide for forming polyimide film for tape automated bonding, substrate for electrical/electronic components, wiring board, insulating film for electrical/electronic components, protective film for electrical/electronic components, display board, touch panel substrate, and substrate for solar cells (all claimed). Uses include but are not limited to inorganic transistor, organic transistor, flexible thin-film transistor, liquid crystal element for display devices, electroluminescent element and photoelectric element.    ADVANTAGE - The polyimide precursor provides polyimide having excellent transparency, heat resistance, solvent resistance and mechanical characteristics, and reduced linear thermal expansion coefficient.    DETAILED DESCRIPTION - A polyimide precursor comprises a repeating unit of formula (I) and a repeating unit of formula (II), and is obtained by thermal imidization. The content of repeating unit (II) is 30-90 mol% with respect to the total content of all the repeating units. 50 mol% or more of total content of bivalent group produced by removing amino group from diamine in repeating units (I) and (II) is a bivalent group of formula (III) and/or (IV).    A=tetravalent group produced by removing carboxy from tetracarboxylic acid;    B'=bivalent group produced by removing amino group from diamine;    X1,X2=H, 1-6C alkyl or 3-9C alkylsilyl;    m1=1-3;    n1=0-3;    V'1,U'1,T'1=H, methyl, or trifluoromethyl;and    Z1, W'1=direct bond, NHCO-, -CONH-, -COO-, or -OCO-.    INDEPENDENT CLAIMS are included for the following:    (1) varnish, which comprises the polyimide precursor;    (2) manufacture of polyimide precursor, which involves heating a tetracarboxylic acid component and a diamine component at 100?oC or more, thermally reacting in a solvent which does not contain a chemical imidation agent, obtaining a reaction solution containing a soluble imide compound including repeating unit (II), adding tetracarboxylic acid component and/or diamine component to the obtained reaction solution, reacting on condition which suppresses imidation to less than 100?oC, and obtaining the polyimide precursor;    (3) polyimide, which is obtained by heat-processing the varnish; and    (4) polyimide film, which is obtained by heat-processing the varnish.