A device for testing body fluids includes (a) a test reagent layer (1) formed on a substrate (5) and containing a test reagent, the tone of which changes according to the content of a test-objective material in a solution to be tested, and (b) a tone layer for criterion (3) formed on the substrate (5) and having a color formed by a dye or the like. The tone layer is used in order to judge the hue of the resulting color of the test reagent layer, wherein both the test layer (1) and the tone layer (3) have the property of absorbing the solution to be tested, and the hue of the resulting color of the test reagent layer and the hue of the tone layer can be compared by their wet colors, thereby affording a highly precise body fluid test.