PURPOSE: To provide an extensive-type diagnostic tool having higher detection sensitivity.

CONSTITUTION: A diagnostic tool is used to judge the presence or absence of a substance to be detected in specimen liquid, a base material 1 is made of materials on which a specimen liquid can be extended and provided with a specimen liquid applying part 2 to which specimen liquid is applied, a first substance carrying part 3 at which a substance to be detected and a first substance that can be specifically bonded with the substance to be detected are carried, and a positivity judgment part 5 at which a second substance different from the first substance that can be specifically bonded with the substance to be detected is carried, further, between the first substance carrying part 3 and the positivity judgment part 5, a specimen extension delaying part 4 for delaying extension of specimen liquid is provided, and/or part of the base materials near the positivity judgment part 5 is provided with a specimen extension disabling part.