A test cell for magnetic immunoreaction assay, comprising a polymer having a quantity of residual magnetism of 15 pT or less, when a magnetic field is applied under a magnetic field of 0.1 T, and with a distance between a sample and a SQUID sensor being set at 1.5 mm, and a method for producing the test cell are provided. A test cell for magnetic immunoreaction assay, comprising a polymer having a metal content of 30 ppb or less, and a method for producing the test cell are also provided. A magnetic signal detected from a magnetic marker to be measured is not buried in or lost to the residual magnetic signal of the test cell itself, but data discrimination can be made clearly.