A semiconductor device tester having a narrow width and small size. A thermostatic chamber (101) having a vertical transfer means, a test chamber (102), and a cooling chamber (103) having a vertical transfer means are arranged in a line. A loader section (300) is provided in front of the chamber (101) and an unloader section (400) is provided in front of the chambers (102 and 103). Therefore, the width of the tester is reduced to a value which is nearly equal to the total width of three test trays.
