An optical measurement apparatus (A) comprising at least one test instrument (B) mounted thereto, the test instrument (B) including a carrier to which a sample is applied, the carrier being provided with at least one reagent retaining portion (8A-8C) for retaining a reagent which develops a color due to a reaction with the sample, the optical measurement apparatus (A) comprising: a reader for reading the color of the reagent at the reagent retaining portion after mounting of the test instrument (B) and before or after a lapse of a reaction completion period, the reaction completion period depending on the reagent, wherein the reader is configured to perform a preliminary reading by reading the color at the reagent retaining portion (8A-8C) at least once after the mounting of the test instrument (B) and before the lapse of the reaction completion period; and a controller for operating and controlling the reader and for making a determination by utilizing data corresponding to the color obtained by the reader , characterized in that the reaction completion period is set based on a test item to be tested by the test instrument (B), in that the determination comprises a positive determination or a negative determination corresponding to a presence or an absence, respectively, of the test item in the sample, in that the controller is configured such that when one of the data corresponding to the color obtained by the reader during the preliminary reading is found to already exceed a reference level Lv, the controller determines the positive determination or negative determination, and finishes a test processing for the test instrument before the lapse of the reaction completion period, wherein the reference level Lv indicates a degree of the reaction progress above which it is possible to make the determination. a reader for reading the color of the reagent at the reagent retaining portion after mounting of the test instrument (B) and before or after a lapse of a reaction completion period, the reaction completion period depending on the reagent, wherein the reader is configured to perform a preliminary reading by reading the color at the reagent retaining portion (8A-8C) at least once after the mounting of the test instrument (B) and before the lapse of the reaction completion period; and a controller for operating and controlling the reader and for making a determination by utilizing data corresponding to the color obtained by the reader , characterized in that the reaction completion period is set based on a test item to be tested by the test instrument (B), in that the determination comprises a positive determination or a negative determination corresponding to a presence or an absence, respectively, of the test item in the sample, in that the controller is configured such that when one of the data corresponding to the color obtained by the reader during the preliminary reading is found to already exceed a reference level Lv, the controller determines the positive determination or negative determination, and finishes a test processing for the test instrument before the lapse of the reaction completion period, wherein the reference level Lv indicates a degree of the reaction progress above which it is possible to make the determination. <EOS>