The present invention provides a urinalysis apparatus easy to maintain and manage without using any supplies such as the test paper, in which the concentration of an optically active substance in urine is determined by measuring the angle of rotation of the urine. Also, a polarimeter and a urinalysis apparatus which are reliable, compact and inexpensive are provided by using a polarimeter including means for transmitting the polarized light through a specimen, applying a magnetic field to the specimen and detecting the change in the direction of light polarization due to the application of the magnetic field.