The present disclosure relates to an underwater thruster, comprising a power part and a propeller, wherein the power part is provided at the upstream of the propeller for driving the propeller to rotate. The underwater thruster further comprises: a water inlet part, which the power part is provided at the upstream or internally of the water inlet part, the water inlet part being provided with a water inlet, one end and the other end of the water inlet part being columnar, and the diameter of radial cross-sections of the water inlet part gradually increasing from one end to the other end of the water inlet part; and a water outlet part, which is provided at the downstream of the water inlet part, one end of the water outlet part being provided with a water outlet, wherein the water inlet part is adjacent to the propeller and provided at the upstream of the propeller, and the propeller is provided inside the water outlet part. According to the present disclosure, by improving the structure of the underwater thruster, the guide stability of the underwater thruster in use is improved, and the kinetic energy utilization rate is increased.