An underwater robot includes a robot body, a roller brush, a walking mechanism, and a gear transmission structure. The roller brush is rotatably disposed at a front end and/or a rear end of the robot body. The walking mechanism is disposed on two sides of the robot body. The gear transmission structure is disposed inside the robot body and is configured to drive the roller brush and the walking mechanism to move. The gear transmission structure includes a fixed shaft and an intermediate transmission gear. The fixed shaft is transversely disposed at a front end of the robot body. The intermediate transmission gear is sleeved on the fixed shaft. A first bearing is sleeved inside the intermediate transmission gear. The fixed shaft is in interference fit with the first bearing.