A coolant supply section that supplies coolant to a main spindle and a coolant recovery section that recovers the coolant from the main spindle are formed in a housing. A coolant flow path that allows the coolant to flow from the coolant supply section to the coolant recovery section is formed in the main spindle. The coolant flow path in the main spindle includes a coolant receiving portion that receives the coolant supplied from the coolant supply section, and a plurality of hole-shaped flow paths formed to extend in the axial direction of the main spindle from the coolant receiving portion. The coolant receiving portion includes an annular groove that is recessed in the outer circumference of the main spindle. The hole-shaped flow paths are formed to extend generally straight toward the coolant recovery section and with an inclination to the radially outer side of the main spindle.