To always such a workpiece safely to be hoisted in good balance even when a sucked surface of the workpiece is in various different sized, and to convey the workpiece.

A plurality of workpiece sucking suckers 20 are provided in a lift carriage 12 liftably suspended in a conveying electric vehicle 1, and a device has a vacuum pump 22a applying a negative pressure to act in each of these suckers 20, workpiece sucked surface size detection means 21 provided with a plurality of sensors 23 detecting a sucked surface Wa of a workpiece W when the lift carriage 12 is lowered down and a switching valve switching a number of the negative pressure acting suckers 20. In the switching valve, only the sucker 20, belonging to a region of size of the sucked surface Wa of the workpiece W discriminated by the workpiece sucked surface size detection means 21, is selectively connected to the vacuum pump 22a.