A self-travelling vacuum cleaner comprising: a body having a suction port; a drive unit which, in operation, moves the body; and an electric fan configured to suck air inside of the body, and a caster provided on a bottom side of the body, wherein the body has two apex parts which define a maximum width of the body, the suction port is disposed on the bottom side of the body, and the caster is disposed at a rear side of the body farther than the drive unit with respect to the part having the maximum width of the body,: wherein the suction port is disposed at a part closer to the part having the maximum width of body than the drive unit and at a position closer to the front side of the outer periphery of body than the center of gravity of self-travelling vacuum cleaner; and wherein each of angles formed between a first tangent and a second tangent and between a first tangent and a third tangent is an acute angle, wherein the first tangent is a tangent of an outer periphery of the body in a plane view and is parallel to a line connecting apexes of the two apex parts of the body, and the second tangent is another tangent of the outer periphery of the body in the plane view and makes contact with the outer periphery at a point on the rear side of the body relative to the line connecting the apexes of the two apex parts of the body, and the third tangent is still another tangent of the outer periphery of the body in the plane view and makes contact with the outer periphery at another point at the rear side of the body relative to the line connecting the apexes of the two apex parts of the body. a body having a suction port; a drive unit which, in operation, moves the body; and an electric fan configured to suck air inside of the body, and a caster provided on a bottom side of the body, wherein the body has two apex parts which define a maximum width of the body, the suction port is disposed on the bottom side of the body, and the caster is disposed at a rear side of the body farther than the drive unit with respect to the part having the maximum width of the body,: wherein the suction port is disposed at a part closer to the part having the maximum width of body than the drive unit and at a position closer to the front side of the outer periphery of body than the center of gravity of self-travelling vacuum cleaner; and wherein each of angles formed between a first tangent and a second tangent and between a first tangent and a third tangent is an acute angle, wherein the first tangent is a tangent of an outer periphery of the body in a plane view and is parallel to a line connecting apexes of the two apex parts of the body, and the second tangent is another tangent of the outer periphery of the body in the plane view and makes contact with the outer periphery at a point on the rear side of the body relative to the line connecting the apexes of the two apex parts of the body, and the third tangent is still another tangent of the outer periphery of the body in the plane view and makes contact with the outer periphery at another point at the rear side of the body relative to the line connecting the apexes of the two apex parts of the body. wherein the suction port is disposed at a part closer to the part having the maximum width of body than the drive unit and at a position closer to the front side of the outer periphery of body than the center of gravity of self-travelling vacuum cleaner; and wherein each of angles formed between a first tangent and a second tangent and between a first tangent and a third tangent is an acute angle, wherein the first tangent is a tangent of an outer periphery of the body in a plane view and is parallel to a line connecting apexes of the two apex parts of the body, and the second tangent is another tangent of the outer periphery of the body in the plane view and makes contact with the outer periphery at a point on the rear side of the body relative to the line connecting the apexes of the two apex parts of the body, and the third tangent is still another tangent of the outer periphery of the body in the plane view and makes contact with the outer periphery at another point at the rear side of the body relative to the line connecting the apexes of the two apex parts of the body.