Abstract: A handler used in a testing system for semiconductors includes an arm shaped conveyer unit for conveying a semiconductor device from a first end thereof to a second end thereof and vice versa,a loader/unloader unit which is provided at the first end of the conveyer unit, a setting unit which is provided at the second end of the conveyer unit, and an adjusting unit for adjusting the setting unit on a testing position which is a predetermined position with respect to a test head. The conveyer unit includes a ring shaped conveyer belt which is rotated between the first end of the conveyer unit and the second end thereof, and a plurality of holders each of which is fixed on an outer surface of the conveyer belt and holds the semiconductor device.