In three-dimensional shape measurement, a backscattered electron detection signal and selection signal generator in a control section controls, by selection signal, a signal switching section and a frame memory so that: detection signals from respective semiconductor elements are sequentially switched in the signal switching section in synchronization with a scanning frame of an electron beam on a sample; and the detection signals from the respective semiconductor elements can be sequentially recorded in recording addresses in the frame memory which correspond to the respective semiconductor elements. After four electron beam scanning sessions, each image data for three-dimensional shape measurement is recorded in the frame memory, and processed in a computing processing section for three-dimensional shape measurement, and the result can be displayed in a display section. The backscattered electron detection signal and selection signal generator in the control section is configured to include, for example, a counter updated in frame scanning units, and can be composed of a very simple circuit or software.