Abstract: The burn-in apparatus according to the present invention comprises a fixing unit for accommodating and fixing a plurality of semiconductor integrated devices and a unit for accommodating the fixing unit with the devices so as to keep a thermal condition therein. The fixing unit and the unit for accommodating the fixing unit are combined as one body to be carryable. The apparatus further comprises a unit for connecting the semiconductor integrated devices with a power supply disposed outside of the apparatus. When a burn-in test is conducted, the fixing unit and the unit for accommodating the fixing unit are combined as one body, and this combined body is fitted with a connector. After the burn-in test is finished, by detaching the unit for accommodating the fixing unit, the fixing unit can be used as trays for conveying the devices to the next test process.