The invention provides a robot zero-point calibration device capable of simply calibrating a zero point of a robot with more than six axes. The robot zero-point calibration device includes an axial position recording unit (14) configured to record positional data of each axis of a robot in each of a plurality of postures when a first positioning point and a second positioning point are made to coincide with each other, the first positioning point being disposed at a predetermined coordinate on a base coordinate system of the robot, and the second positioning point being disposed at a predetermined coordinate on a flange coordinate system of the robot. The device also includes a positional offset calculating unit (15) configured to calculate an offset amount of a zero point of each axis ofthe robot from a true zero point of the axis based on a plurality of sets of the positional data stored in the axial position recording unit (14).