1. A parts supply device comprising:a robot attachment member configured to be attached to a distal end portion of a robot arm;
a pair of claws which are supported by the robot attachment member and which are moved toward and away from each other by a first actuator;
a vacuum member which is supported by the robot attachment member and which is connected to a compressor via a pipe so that a tubular stick containing parts aligned in a direction is mounted on the vacuum member when the compressor sucks air;
a guide slider that receives the parts from the stick mounted on the vacuum member and guides the parts
to a holding position at which one of the parts can be held by the pair of claws; and
a second actuator which moves the guide slider from a first position, in which the one of the parts is guided to the holding position by the guide slider, to a second position, in which the guide slider is apart from the one of the parts which is held by the pair of claws so that the one of the parts held by the pair of claws can be mounted on or supplied to a predetermined position.