PURPOSE: To easily determine tannin in liquors by impregnating reagents the coloration of which is caused by tannin in filter paper, using this filter paper as test paper, dropping the liquors onto the paper and measuring the formed color tone.

CONSTITUTION: The reagents which are colored by reacting with tannins, for example, heavy metals (ferric chloride, etc.) or alkaloids are impregnated into the filter paper to prepare the test paper. The calibration curve by absorbancy is first determined in accordance with the Folin-Dennis method of a tannin determination method and the spectral chart of the coloration corresponding thereto is prepd. The liquors are then dropped on the test paper by a squirt to allow the test paper to color. The formed color tone is contrasted with the color tones of the spectral chart and the digital number corresponding to the color tone is read, by which the content of tannin is colorimetrically determined. The content of tannin contained in the liquors is, therefore, easily measured and the decision of a good body and flavor is enabled.