An electrode inspection apparatus for spot welding is provided for precisely measuring diameters of a tip of an electrode without reducing availability ratio in a production line, and is particularly useful when inspecting a weld gun having electrodes with a narrow distance therebetween.A CCD camera 91 for imaging the tip of the electrode held to the weld gun is disposed in an inspection apparatus body 6. The inspection apparatus body 6 includes a measuring reference unit 7 in which a fixing hole 72a for fixing the tip of the electrode is formed, and a mirror 8 obliquely arranged with respect to the electrode so as to be distant from the fixing hole 72a at a position opposite to the electrode with respect to the measuring reference unit 7. The CCD camera 91 is disposed in a side of the mirror 8 with a distance therebetween for imaging the tip of the electrode from a direct front thereof reflected on the mirror 8 by reflection.