PURPOSE: To enable high-speed processing with a biochemical analyzer using a long-sized test film by specifying the length of an incubator and the distance from the inlet of the incubator to a measuring means to suitable lengths and moving the film back and forth.

CONSTITUTION: A sample is spotted by a spotting nozzle 15 onto the long-sized test film 3 and the film is intermittently fed by a length l each into the incubator 55 and the degree of the coloration thereof is measured by the measuring means 57. The length L of the incubator 55 and the distance M from the inlet of the incubator 55 to the measuring means 57 are specified to equation I and equation II [where (nt+1) is the max. integer without exceeding nt+1] when the time required for the incubation is designated as (t) and the number of spotting times per unit time as (n). The film 3 is moved back and forth in such a manner that the spotted part comes to the position of the measuring means 57. The time for the incubation is thereby prevented from hindering the high-speed processing regardless of an end point method and speed method.