PURPOSE: To provide a vacuum microdevice of a structure for restoring the device to a separated position other than when necessary by removing weak points for an external surge, and by forming a correlated location for each electrode as required.

CONSTITUTION: Inner parts 7 of an emitter 2 as well as a collector 3 are in contact with the inside of a vacuum glass tube 5 in the same manner as a read switch 11, while the emitter 2 in the glass tube 5 and the front end part of the collector 3 are overlapped on one another. Parts 2c and 3c that are close to the counter ends are sealed, and intermediate parts 2b and 3b are provided with resiliency. A gate 4 is interposed between the emitter 2 and the collector 3 to form a structure as a microdevice, and the sealed part 3c and a point 4c of the gate 4 and the collector 3 are insulated by ceramic and the like, while an intermediate part 4b of the gate 4 is formed into a thin film, not to inhibit the resiliency of the collector 3.