Method and apparatus capable of well observing or inspecting a liquid sample (20). The apparatus, for example a scanning electrode microscope, can be maintained and serviced better than heretofore. The apparatus has a film (32) including a first surface (32a) to hold the liquid sample (20) thereon, a vacuum chamber (11) for reducing the pressure of an ambient in contact with a second surface (32b) of the film (32), primary beam irradiation means (1) connected with the vacuum chamber (11) and irradiating the sample with a primary beam (7) via the film (32), signal detection means (4) for detecting a secondary signal produced from the sample (20) in response to the beam irradiation (7), a partitioning plate (14) for partially partitioning off the space between the film (32) and the primary beam irradiation means (1) in the vacuum chamber (11), and a vacuum gauge (15) for detecting the pressure inside the vacuum chamber (11).
Damage to the film is detected by a pressure increase inside the vacuum chamber. After detecting such a pressure increase the partitioning member is moved in the path of the irradiating beam in order to prevent sample material to spill into the irradiation means.