An automatic chemical analyzing apparatus including a cuvette assembly having a plurality of rows of reaction tubes arranged in respective sample magazines, each sample magazine being conveyed sequentially in a direction perpendicular to the transverse row of reaction tubes, and then in a direction parallel thereto so as to complete a reaction channel, during which the samples to be analyzed in the magazine are treated and analyzed a predetermined number of times by passing through a photometer. Adjacent the reaction channel is provided a preparation channel for cleaning and drying of reaction tubes and/or for adding of samples and reagants to the cleaned and dried tubes. Sample magazines are selectively transferrable from the reaction chamber to the preparation chamber upon completion of testing of the samples.