A spindle assembly of a machine tool includes a rotating body for holding a tool, a bearing, a housing supporting the rotating body rotatably about a first axis via the bearing, a supply flow channel supplying oil and air to the bearing, and a collecting flow channel collecting the oil through the bearing. The rotating body includes a first portion supporting the bearing and having a first outer circumferential surface, a second portion having a second outer circumferential surface, and a stepped surface connecting the first and second outer circumferential surfaces. The housing includes a third portion supporting the bearing, and a fourth portion defining an annular receiving space receiving the oil. The fourth portion includes an opening portion guiding the oil to the collecting flow channel, and an annular projection facing the stepped surface and the annular receiving space and projecting in a direction away from the first axis.

A spindle lubricator of a machine tool includes a rotation body configured to hold a tool; bearings; a housing; a fluid mixture supplier; and a collector that collects an oil-containing fluid. The collector includes collection flow channels, ejectors, and flow control valves. The ejectors include a first ejector configured to generate negative pressure due to first air to suck a first oil-containing fluid through a first collection flow channel; and a second ejector that generates negative pressure due to second air to suck a second oil-containing fluid through a second collection flow channel. The flow control valves include a first flow control valve configured to adjust a flow rate of the first air; and a second flow control valve configured to adjust a flow rate of the second air.