A fixing structure includes a battery post terminal having extended portions each having an inclined surface formed thereon, and an electrode fitting part sandwiching, from both sides, side surfaces of a battery post by performing pressing to narrow a space between the extended portions; a slope member having four leg parts each having a slope formed thereon whose inclination angle is the same as that of the inclined surface, and pressing the extended portions by being moved in an up-and-down direction while making the slopes to be brought into contact with the inclined surfaces; and a bolt moving the slope member in the up-and-down direction, in which the four leg parts are disposed with a space provided therebetween along an outer periphery of a screw part, the screw part being set as a center, when the battery post terminal is seen from a vertical direction.