NOVELTY - The apparatus (1) has a dissolving device (2) which dissolves a thickener as powder that is ionized when dissolved in a liquid solvent. A dissolution-rate-to-solubility determining device (25) is provided to measure conductivity of the solution of the thickener dissolved by the dissolving device and is provided to determine a dissolution rate to solubility of the solution of the thickener based on the measured conductivity.    USE - Apparatus for manufacturing electricity storage material such as materials for capacitors for lithium ion secondary batteries used for hybrid vehicle and electric vehicle.    ADVANTAGE - The dissolution rate to solubility of the solution of the powder thickener dissolved in the liquid solvent is measured easily. The dissolution rate to solubility of the solution of the thickener is determined without the need to stop the dissolving device during dissolution of the thickener in the liquid solvent. This can prevent excessive operation of the dissolving device, and can therefore achieve energy saving. The dissolution using microwaves reduces the time required, so that less electric power is required. The damage state of the particles of the active material due to kneading is predicted before actual kneading, so that kneading is performed such that the particles of the active material are not damaged. Thus damage to the active material is suppressed efficiently. The dissolution of the thickener, adjustment of the viscosity of the solution of the thickener, and dispersion and kneading of the powder of the active material are performed simultaneously, so that production efficiency is improved.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a method for manufacturing electricity storage material.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of the apparatus for manufacturing electricity storage material.    Apparatus (1)    Dissolving device (2)    Manufacturing control device (5)    Solubility determining device (25)    Viscosity estimating device (56)