The invention relates to semiconductor technologies, and particularly relates to a transverse constant current diode. The transverse constant current diode provided by the invention forms a P-type well region through introducing a lightly doped P-type region and a heavily doped P-type region into an N-type well region, thereby modulating a surface electric field, and improving breakdown voltage. Meanwhile, the lightly doped P-type region can assist to exhaust the N-type well region, thereby enabling a channel to be pinched off more easily, coming into a constant current region quickly, enabling the constant current diode to have lower pinch-off voltage, shortening the channel length of the deep heavily doped P-type region, and improving the constant current of the constant current diode. The transverse constant current diode has the beneficial effects that the breakdown voltage of the transverse constant current diode is improved effectively, the channel is enabled to be pinched off more easily at the same time, the constant current region can be entered quickly, the transverse constant current diode is enabled to have lower pinch-off voltage, and the constant current of the transverse constant current diode is effectively improved. The transverse constant current diode provided by the invention is especially applied to transverse constant current diodes.