A transmission circuit according to an embodiment includes: a plurality of constant current circuits, a plurality of switching elements, and controlling circuitry. The plurality of constant current circuits are connected in parallel to a power source line connected to a single power source and a transducer element. Each of the plurality of switching elements is connected to a different one of the plurality of constant current circuits and to the transducer element. The controlling circuitry is configured to control the plurality of switching elements on the basis of a waveform signal indicating a waveform of an ultrasound wave output from the transducer element.