A grinder comprising: a body which has a collar (62; 162); a wheel cover which is attachable to the collar (62; 162); and a holding member (70; 170) which is adapted to hold the wheel cover fixedly to the collar (62; 162), wherein the wheel cover has an annular shaped attachment portion which is attachable to the collar (62; 162), wherein the holding member (70; 170) has an engagement portion (71; 171) and an engagement portion operating member to move the engagement portion (71; 171), the engagement portion (71; 171) being engageable with the attachment portion, wherein the engagement portion operating member switches a state between an engagement state in which the attachment portion and the engagement portion (71; 171) are engaged to each other and a disengagement state in which the attachment portion and the engagement portion (71; 171) are disengaged to each other by moving the engagement portion (71; 171), wherein the engagement portion operating member moves on a second line (L2; L12) which is parallelly offset from a first line (L1; L11) passing a center of the attachment portion and extending in a predetermined direction, wherein the holding member (70; 170) has a biasing member which biases the engagement portion operating member, and wherein the engagement portion operating member is adapted to cancel an engagement between the attachment portion and engagement portion (71; 171) by moving against a biasing force of the biasing member, characterized in that the engagement portion operating member is located at a tangent line region which corresponds to a tangent line parallel to the first line (L1; L11), and wherein the engagement portion operating member moves linearly along the tangent line, a recess (66; 166) is provided on the collar (62; 162), the recess (66; 166) extending along a circumference direction of the collar (62; 162) at a predetermined position in an axial direction of the collar (62; 162), and the holding member (70; 170) is movable in a radial direction of the collar (62; 162) inside the recess (66; 166), and is regulated to move in an axial direction of the collar (62; 162) by engaging with the recess (66; 166). a body which has a collar (62; 162); a wheel cover which is attachable to the collar (62; 162); and a holding member (70; 170) which is adapted to hold the wheel cover fixedly to the collar (62; 162), wherein the wheel cover has an annular shaped attachment portion which is attachable to the collar (62; 162), wherein the holding member (70; 170) has an engagement portion (71; 171) and an engagement portion operating member to move the engagement portion (71; 171), the engagement portion (71; 171) being engageable with the attachment portion, wherein the engagement portion operating member switches a state between an engagement state in which the attachment portion and the engagement portion (71; 171) are engaged to each other and a disengagement state in which the attachment portion and the engagement portion (71; 171) are disengaged to each other by moving the engagement portion (71; 171), wherein the engagement portion operating member moves on a second line (L2; L12) which is parallelly offset from a first line (L1; L11) passing a center of the attachment portion and extending in a predetermined direction, wherein the holding member (70; 170) has a biasing member which biases the engagement portion operating member, and wherein the engagement portion operating member is adapted to cancel an engagement between the attachment portion and engagement portion (71; 171) by moving against a biasing force of the biasing member, characterized in that the engagement portion operating member is located at a tangent line region which corresponds to a tangent line parallel to the first line (L1; L11), and wherein the engagement portion operating member moves linearly along the tangent line, a recess (66; 166) is provided on the collar (62; 162), the recess (66; 166) extending along a circumference direction of the collar (62; 162) at a predetermined position in an axial direction of the collar (62; 162), and the holding member (70; 170) is movable in a radial direction of the collar (62; 162) inside the recess (66; 166), and is regulated to move in an axial direction of the collar (62; 162) by engaging with the recess (66; 166).