PURPOSE: To shorten the index time by conveying a test tray to the first stopper position of a test head, testing only odd rows of a device to be tested, conveying the test tray to next stopper position, and testing even rows.

CONSTITUTION: For example, eight devices 16 to be tested are arranged in the length L of a test tray 11 while the gas between the devices being narrowed to the limit. The tray 11 are conveyed to a stopper 19 of a test head by a conveying system, the devices 16 are made to have electric contact, and only odd rows of the devices 16 are tested. After the finish of the test, the projected part of the stopper 19 is withdrawn and the tray 11 is conveyed to the position of a stopper 101, fixed there, and only even rows of the devices 16 are made to have electric contact and tested. The conveyed distance at that time is equal to the distance Z between the stoppers 19 and 101. After the finish of the test, the stopper 101 is withdrawn, the tray 11 is conveyed to a discharge part. The conveyed distance is equal to L-Z. The index time per one device becomes L/8 s (s stands for conveying speed) and consequently is shortened by a half of the time needed conventionally.