To provide a technique for elevating/lowering a platform even when one of a plurality of actuators fails to operate.

A plurality of actuators 20 and 30 are placed in parallel in the same direction. End parts of rods 24 and 34 of the respective actuators 20 and 30 are joined to an attachment member 55 including a second member 50 and the end parts of bodies 22 and 32 are connected to one ends of crank mechanisms 60 and 70. The other ends of the crank mechanisms 60 and 70 are fixed to a horizontal member 44 for constituting a first member 40. Thus, in an elevating/lowering device 1, even when either of the plurality of actuators 20 and 30 fails and stops and the other of normal actuators 20 and 30 keeps expanding, the crank mechanisms 60 and 70 open, so that it does not occur that the actuators 20 and 30 and a first member 40 stop in a state where they are engaged at a joint part, or that the actuators 20 and 30 are broken.