A housing of a pump unit is fixed to a drape of a wound dressing by a joint portion. A suction chamber that is brought into a negative pressure by driving of a piezoelectric pump directly communicates with a closed space through an opening and an inlet. Hence, a therapy device does not need to include a pipe that allows the closed space and the pump unit to communicate with each other. Therefore, since the therapy device does not need to include the pipe that allows the pump unit to communicate with the closed space, detachment of the pump unit from the wound dressing owing to coming-off of the pipe is avoided. Since the housing is fixed to the drape by the joint portion, the pump unit can be prevented from detaching from the wound dressing.