A constant angular grinding tool comprising: a profile wheel whose grinding face is fixed at an inclination angle with respect to the axis of a spindle of a rotary electric tool; a first guide plate which is a disc member attached rotatably to a spindle between the profile wheel and the rotary electric tool so as to guide for a grinding direction by bringing the edge of the disc member into a contact with the reference level of a material; and a second guide plate which is a disc member attached rotatably to a spindle between the profile wheel and the first guide plate and whose outer peripheral end face makes contact with the edge of the material to control a grinding distance from the edge.