A height adjustable desk includes a worksurface, a control module, and at least a leg module. The control module has a control circuit and a control panel electrically connected to the control circuit. The leg module has a first leg member, a second leg member and, a driving device. The first leg engages the second leg member for reciprocation. The second leg member is fixed with a block with a threaded hole. The driving device has a motor electrically connected to the control circuit and a screw rod connected to a spindle of the motor and screwed into the threaded hole of the block. When a user operates the control panel, the control circuit commands the motor to rotate the screw rod accordingly to lift or lower the work surface.