A measuring device (100a) includes a base body (101) constituting: a sample holding portion (102) configured to hold a test sample containing urea and a material to be detected; and a sample supply port (103) through which the test sample is supplied to the sample holding portion (102). The base body includes an optical measuring portion and a reagent holding portion (111) which are configured to carry out an optical measurement of the test sample held by the sample holding portion (102). The reagent holding portion holds an antibody to the material to be detected and urease which causes hydrolysis of the urea. With this, the present invention provides a measuring device, a measuring apparatus, and a measuring method, each having a simple configuration and capable of reducing measurement errors caused by the urea contained in the test sample and accurately measuring the material to be detected.