To provide an automatic winder in which a switching operation of an operation/stop switch of each winding device before and after a yarn supplying bobbin preparing operation can be omitted.

The automatic winder 100 includes: a plurality of winding devices 10 for winding a yarn Y from a yarn supplying bobbin B1 to form a package P by an automatic operation; and a machine base control body 5 for controlling an operation of the plurality of winding devices 10. The winding device 10 includes an automatic operation switch 12 for switching execution or stop of a winding operation by automatic operation, and the machine base control body 5 includes a control section 50 for causing transition to a yarn supplying bobbin preparing mode realizing a state in which a preparing operation of the yarn supplying bobbin B1 is executable regardless of a switching state of the automatic operation switch 12 of the plurality of winding devices 10.