A test object receptacle, capable of measuring a test object in a wide range of concentrations with good accuracy and within a short time, contains a plurality of fine protruding portions inside grooves. The test object receptacle can fix antigens, antibodies and test objects faster than without the protruding portions. Furthermore, the protruding portions are so formed that the surface area thereof increases gradually to the downstream with respect to the movement direction of the test object in the grooves, the detection intensity (intensity of color development) of the test object is not saturated downstream of the grooves even when the test object has a high concentration. For this reason, the test object can be detected within a short time and the measurements can be conducted within a wide concentration range.