Ion milling device and processing method using the ion milling device

This ion milling device is provided with a vacuum chamber (105), an exhaust device (101) for evacuating the interior of the vacuum chamber, a sample stage (103) for supporting a sample (102) to be irradiated inside the vacuum chamber, a heater (107) for heating the interior of the vacuum chamber, a gas source (106) for introducing into the vacuum chamber a gas serving as a heating medium, and a controller (110) for controlling the gas source, the controller controlling the gas source so that the vacuum chamber internal pressure is in a predetermined state during heating by the heater. This enables the control in a short time of the temperature for suppressing condensation, or the like, occurring at atmospheric release after cooling and ion milling a sample.