A positioning apparatus and a working system which can position a workpiece with better accuracy at a lower cost and in a reduced space even when the workpiece is heavy are provided. The positioning apparatus has 3 robot arms (1)-(3) each having an arm and an actuator which drives the arm, a mounting platform (5) which is supported by the ends of the three robot arms (1)-(3), a securing jig (6) which secures a workpiece W which is mounted on the mounting platform (5) to the mounting platform (5), and a controller (9) which controls the operation of each of the actuators.