A simple membrane assay method wherein an analyte of test sample is assayed with the use of an assay unit including a membrane having, bonded thereto, a trapping reagent for capturing the analyte, which method is characterized in that a test sample is filtered through a filter and thereafter dropped on the membrane to thereby detect the presence of analyte in the test sample. There is further provided a simple membrane assay kit for checking the presence of analyte in a test sample, which assay kit comprises (1) a filter and (2) an assay unit including a membrane having, bonded thereto, a trapping agent for capturing the analyte. Thus, there can be realized a simple test for rapidly checking on site any analyte, such as a pathogenic organism or an antibody, in a test sample collected from medical spots and individuals, in which the occurrence of false positive is prevented, enabling high-precision detection of the analyte.