PURPOSE: To detect a very minute amount of contaminant by forming a hydrofilic film on the surface of a planar body, dropping liquid droplets, measuring the initial contact angle, leaving the film alone in an atmosphere to be inspected, and measuring the contact angle of the liquid droplet again.

CONSTITUTION: The surface of a silicon (Si) plate 10 has the adsorptivity. The surface is polished. The silicon plate 10 undergoes SC1 treatment. The interface state of an SiO2 film 11 has the hydrophilic property. An inspecting plate 12 on which the SiO2 film 11 is formed is prepared. Water droplets 13 are dropped on the surface of the inspecting plate 12, and an initial contact angle θ1 is measured. Then, the droplets are removed, and the inspecting plate 12 is left alone in a clean room for fabricating semiconductors for about one week. Then, water droplets 13 are dropped again on the upper surface of inspecting plates 12A and 12B. After the plates are left alone, the contact angle θ2a and θ2b are measured. The differences between the initial contact angle θ1 and the contact angles θ2a and θ2b after the plates are left alone are inspected. When the difference is found, it is judged that the very minute amount of the contaminant is contained in the atmosphere.