To provide a water level detection device for a plumbing equipment capable of detecting a water level of the plumbing equipment by utilizing a water level sensor using an ultrasonic wave whereby a drainage pump or the like can be surely driven.

In this water level detection device, an ultrasonic wave oscillation element is driven in the air toward a water surface to be measured and the reflection wave from the water surface is detected so that the water level is measured. A head 1 having the ultrasonic wave oscillation element and a receiving element is supported by one end of a cylindrical body 2 and openings 21, 22, 23, 24 are provided on a wall of the cylindrical body 2 in relation to a reference water level. An opening end of the cylindrical body 2 is dipped into a water to be measured to be submerged below the water surface and is fixed thereto. The openings 21, 22, 23, 24 are provided in connection with an operation region and a non-operation region of a pump 4 as an object to be controlled by this detection device. When the water does not exist in the openings, an ultrasonic wave reflection article is inserted from one of them to form a dummy water surface so that it is possible to allow it to be an opening for testing the operation or non-operation of the object to be controlled.