A rotary table device includes: a case; a spindle having an axis hole that is provided rotatably in the case and extends through along an axis direction of a center portion; a rotary joint having a rotary shaft attached non-rotatably to the axis hole of the spindle; and a clamp mechanism arranged in a rear end side of the case and having a component attached non-rotatably to the spindle, the rotary shaft having an attachment flange unit with the spindle in a front end portion, the rotary shaft inserted to the axis hole from the front end side of the spindle to be attached to the spindle by the attachment flange unit, a rear end portion of the rotary shaft projecting from a rear end surface of the spindle, the component of the clamp mechanism mounted to a rear end portion of the rotary shaft projecting from the rear end surface of the spindle from a rear end side, and contacting with and externally fit to an outer circumferential surface of the rear end portion.