PURPOSE:To shorten the exchanging time without requiring to stop rotation of a main spindle and improve the operation efficiency of a machine tool by synchronizingly rotating an exchanging tool or a tool housing at a tool exchange for a tool main spindle of ended working, and making relative stopped condition between both. CONSTITUTION:By mutually approaching a tool main spindle 14 and a tool magazine 32 in the vertical direction and simultaneously synchronizingly rotating a tool housing 34 in the same direction, relative stopping condition between the main spindle 14 and the housing 34 is established. Next, after approaching both, a tool 20 is dropped and fixed in the empty housing 34 by releasing the tool 20 mounted on the tool mounting part 14b of the main spindle 14 under a draw bar 18. Mutually approaching a next housing 34 receiving a tool 20 to be used and the main spindle 14, rotating speed of both are synchronized, and by further approaching the taper shank 20a and the pull stud 20b of the tool 20 in the housing 34 are introduced into the tool mounting part 14b of the main spindle 14. Nextly, at reaching the condition capable of mounting, the tool 20 is mounted on the tool mounting part 14b of the main spindle 14 by releasing pushdown of the draw bar 18.