Abstract: A simplified measuring apparatus for use in the qualitative or quantitative measurement of substances to be assayed in test samples, such as proteins, antibodies and the like, in a small amount of test samples by a simple and easy operation without requiring a B/F separation step comprises: (a) a liquid permeable porous reaction membrane whose surface having at least one reaction area to which an affinity substance capable of directly or indirectly capturing a substance to be assayed or a soluble agent is immobilized; (b) a porous body arranged on the upper part of the porous reaction membrane, to which a soluble agent capable of being solubilized by the addition of a test sample is adhered in a releasable manner; (c) an absorption member arranged on the lower part of the porous reaction membrane, which contacts with a periphery, excluding the reaction area, of the porous reaction membrane via a liquid non-permeable sheet; (d) a liquid non-permeable transparent cover arranged on the lower part of the absorpti