High resolution observation of a sample at a high temperature above 1000° C. is accomplished by suppressing sample drift by heating over a short time and with small electric current. A heater envelope made of a ceramic having a carbon coating on the surface is attached around a heater surrounding the sample. The heater envelope is rotatable around pivot screws, and has an outer frame portion of a holder individually having slots capable of letting an FIB enter so that the sample mounting on the holder, as it is, may be milled with the FIB.