To obtain the subject reagent which is diluted in use, reacted with an enzyme, etc., in a specimen to form a target measuring substance, has a long preservation period and is capable of measuring a large amount of specimens, by concentrating a first and a second reagents in a state in which the components of both the reagents maintain constituent ratios, respectively.

In a biochemical reagent which comprises a first and a second reagents, is reacted with a specific enzyme or substance in serum or urine as a specimen to form a fixed measuring object, the first and the second reagents are adjusted to a concentrated state in which both the reagents maintain the constituent ratios of constituent components constituting the reagents. Just before use, the biochemical reagent is diluted with diluting water and adjusted for use to give the objective liquid concentrated biochemical reagent which has a long preservation period, is capable of measuring a large amount of specimens with a small volume and is useful for measuring AST (aspartate aminotransferase), ALT (alanine aminotransferase), LDH (lactate dehydrogenase), ALP (alkaline phosphatase), etc.