NOVELTY - A solid catalyst (I) comprises alkali metal cation, divalent metal cation, trivalent metal cation and halogen anion.    USE - Solid catalyst is used for producing biodiesel (claimed).    ADVANTAGE - The solid catalyst efficiently provides biodiesel in short of time, without alkaline discharge.    DETAILED DESCRIPTION - A solid catalyst comprises alkali metal cation, divalent metal cation, trivalent metal cation and halogen anion, and is of formula: C'y/M2+1-x(M3+)xO/Ax+y (I).    C'=alkali metal cation;    M2+=divalent metal cation;    M3+=trivalent metal cation;    A=halo anion;    x=0.2-0.24;and    y=0.06-0.1.    INDEPENDENT CLAIMS are included for the following:    (1) preparation of solid catalyst. Divalent metal oxide and trivalent metal oxide are mixed in the molar ratio of 3-4:1 to obtain solution of catalyst component. Ammonium halide, hydroxide and ammonia are mixed to obtain alkaline solution. The obtained alkaline solution and catalyst component are mixed thoroughly, stirred in an autoclave, and hydrothermally treated for 5-7 hours. The resultant mixture is subjected to reduced spin steam dehydration, dried at 40-50 degrees C, and modified using an alkali metal and halogen to obtain solid catalyst precursor. The obtained precursor is calcined in nitrogen atmosphere for 5-8 hours, and temperature is controlled at 250-600 degrees C to obtain solid catalyst; and    (2) application of solid catalyst for producing biodiesel. Oil and low-carbon alcohol are mixed in the molar ratio of 4-5:1, added to three-necked flask equipped with a reflux apparatus, stirred, added solid catalyst and reacted for 2-4 hours after increasing temperature to 50-100 degrees C. The mixture is separated, such that upper layer containing biodiesel and lower layer containing unreacted alcohol are collected. The upper layer containing biodiesel is then vacuum-distilled, separated and lower alcohol is recovered to obtain biodiesel. The total content of oil and low-carbon alcohol is 0.1-0.2 wt.% with respect to content of catalyst.