Rotary driving device

A rotary driving device comprising:

• a shaft which has one end and the other end in an axial direction and is provided with an oil passage through which lubricating oil flows from the one end to the other end;
• a transmission case accommodating the shaft therein;
• and
• a bearing arranged at the other end of the shaft and rotatably supporting the shaft,
• the shaft including an end surface located on the other end in the axial direction,
• the transmission case including an opposing surface facing the end surface with a gap therebetween in the axial direction, and
• one of the end surface and the opposing surface being provided with a groove so as to generate a negative pressure on the other end when the shaft rotates to suck the lubricating oil through the oil passage towards the other end.