Abstract: A coolant through spindle device is disclosed, including a rotating joint member secured to the rear end of the spindle for conducting coolant into the spindle, the coolant being conducted through a separate coolant passage inside the spindle to the nozzles formed on a cutting tool to be sprayed out thereof so as to fully cool down and lubricate the cutting point thereof, increase machining precision and cutting rate, and prolong service life of the cutting tool. Moreover, by using a switching collar to provide separated coolant passage and pressurized air passage, no residual coolant can follow the pressurized air jet into the tapper hole of the spindle to contaminate the tapper hole.