To provide a tool measuring device and a tool measuring method capable of accurately measuring a phase angle of the cutting edge tip for imparting a maximum outer diameter of a rotary cutting tool.

This tool measuring device has a spindle head 12 for rotatably supporting the rotary cutting tool T, a servomotor for rotating the rotary cutting tool T, a rotary encoder 18 for detecting a phase angle around the axis of the rotary cutting tool T, and optical sensors 24 and 25 for outputting a signal corresponding to respective outer diameters of the rotary cutting tool T. The rotary cutting tool T is positioned in a plurality of phase angle positions around the axis A. A tool outer diameter measured by the optical sensors 24 and 25 is associated with respective positions of the plurality of phase angle positions. The phase angle position for imparting the maximum outer diameter of the rotary cutting tool T, is arithmetically operated by a least square method.