Abstract: Disclosed is a method with which it is possible to observe a biological sample in a living state, without significant restrictions due to the properties of the sample or due to a structural body accommodating the sample. To observe a target sample on a sample stage using a SEM including a radiation source for electron beam irradiation, the method includes: a step of bringing an insulating and electron-permeable thin film into contact with the target sample in such a way as to follow a surface on the radiation source side of the target sample, and sealing the target sample in a gap between the film and the sample stage; and a step of radiating an electron beam onto the target sample from the radiation source through the film.