PURPOSE: To facilitate centering of a device for detecting a tool breakage of a working head in a turret apparatus in which plural working heads are divided round a horizontal shaft, and a working head divided in a dividing position is installed on the front of a slide unit.

CONSTITUTION: Four working heads 10A, 10B, 10C, 10D are provided on a revolving body 7 of the forward end of a revolving shaft 6, a support shaft 51 is inserted in the center of rotation of the revolving shaft 6 in such a manner as to freely move forward and backward, a support base 57 is fitted to the tip projecting part 51a of the support shaft 51, and a tool breakage detecting device 50 is fixed on the support base opposite to a working head 10C put in an upper revolving position C. As the center of rotation of the revolving shaft 6 is taken as a common reference, centering of a detecting element 61a or the like to a tool T can be facilitated.