An optical measurement apparatus is provided for conducting a test by efficiently reading color development of a reagent after reaction by optical measurement.To the above end, an optical measurement apparatus is provided which is to be used with at least one test instrument mounted to the apparatus. The test instrument includes a carrier provided with at least one reagent retaining portion which retains a reagent, and a sample is applied to the carrier. The optical measurement apparatus includes a reader for reading color development of the reagent retaining portion, and a controller for performing driving control of the reader and determination. The controller performs the determination by utilizing data obtained by a reading operation P to read the color development of the reagent performed after the lapse of a reaction completion period Tr1-Tr6 from the mounting of the test instrument, and the reaction completion period depends on the reagent.