An electrical device to be fitted into an opening of a panel and fastened to the panel, the electrical device comprising: a housing including a front portion to be positioned frontward from the panel and a back portion to be positioned backward from the panel when the electrical device is fastened to the panel; and an electrical device fastener configured to install the housing onto the panel in a removable manner, wherein the electrical device fastener is attached to the housing in a rotatable manner to move between a first position enabling the housing to be installed onto the panel and a second position disabling the housing to be installed onto the panel, the housing includes, on a contour surface thereof, a flange extending outwardly, and the electrical device fastener includes a base having a screw-receiving hole, and a screw that is screwed with the screw-receiving hole, characterized in that: the housing includes, on a contour surface thereof, a shaft extending in a contour direction of the housing, the electrical device fastener includes an engagement part that extends from the base and is engaged with the shaft in a rotatable manner, when the electrical device fastener is at the first position, an end of the screw faces the flange, and when the electrical device fastener is at the second position, the end of the screw does not face the flange, the housing includes a movement restricting part that is adapted to restrict backward movement of the base when the electrical device fastener is at the first position, and wherein the electrical device is configured such that when, in the electrical device fitted in the opening of the panel, the electrical device fastener is moved from the second position to the first position and the screw is screwed into the base, the movement restricting part restricts backward movement of the base to cause an edge of the opening of the panel to be sandwiched between the flange and the screw and thereby install the housing onto the panel with the electrical device fastener and fasten the electrical device to the panel. a housing including a front portion to be positioned frontward from the panel and a back portion to be positioned backward from the panel when the electrical device is fastened to the panel; and an electrical device fastener configured to install the housing onto the panel in a removable manner, wherein the electrical device fastener is attached to the housing in a rotatable manner to move between a first position enabling the housing to be installed onto the panel and a second position disabling the housing to be installed onto the panel, the housing includes, on a contour surface thereof, a flange extending outwardly, and the electrical device fastener includes a base having a screw-receiving hole, and a screw that is screwed with the screw-receiving hole, a base having a screw-receiving hole, and a screw that is screwed with the screw-receiving hole, the housing includes, on a contour surface thereof, a shaft extending in a contour direction of the housing, the electrical device fastener includes an engagement part that extends from the base and is engaged with the shaft in a rotatable manner, the electrical device fastener includes an engagement part that extends from the base and is engaged with the shaft in a rotatable manner, when the electrical device fastener is at the first position, an end of the screw faces the flange, and when the electrical device fastener is at the second position, the end of the screw does not face the flange, the housing includes a movement restricting part that is adapted to restrict backward movement of the base when the electrical device fastener is at the first position, and wherein the electrical device is configured such that when, in the electrical device fitted in the opening of the panel, the electrical device fastener is moved from the second position to the first position and the screw is screwed into the base, the movement restricting part restricts backward movement of the base to cause an edge of the opening of the panel to be sandwiched between the flange and the screw and thereby install the housing onto the panel with the electrical device fastener and fasten the electrical device to the panel.