A motor apparatus having a motor section (20; 120; 220) and a connector unit (40; 150; 250) connectable to an external connector for supplying driving current to the motor section, the motor apparatus comprising: a motor case (21; 121; 221) formed into a bottomed cylindrical shape; four magnets (22; 122; 222) each formed into an approximately arc shape in cross section; a rotator (23; 123; 223) rotatably provided in an internal space formed by the four magnets; an armature shaft (24; 124; 224) axially aligned with the rotator and fixed to the rotator; and a commutator (25; 125; 225) fixed to an approximately central portion of the armature shaft along an axial direction of the armature shaft, wherein the motor case has a side wall portion to which the four magnets are attached, the side wall portion being composed of a pair of arc-shaped portions (121a; 221a) and a pair of straight portions (121b; 221b), the straight portions intervening between the arc-shaped portions, the four magnets are respectively arranged in the vicinity of four corners between the arc-shaped portions and the straight portions, each of the four magnets has a thick portion and two thin portions smaller in thickness than the thick portion, the thin portions being integrally formed on both sides of the thick portion in the circumferential direction of the motor case, wherein the arc-shaped portions and the straight portions are respectively formed so as to extend from an opening portion side of the motor case to a bottom portion side thereof, the straight portions respectively have flat inner faces parallel to each other, the arc-shaped portions respectively have arc-shaped inner faces, the arc-shaped inner faces being arranged so as to sandwich and face the armature shaft, and the arc-shaped inner faces and the flat inner faces respectively extend along the axial direction of the armature shaft, in a diametrical direction of the armature shaft, one of the flat inner faces is partially overlapped with parts of two magnets, and the other of the flat inner faces is partially overlapped with parts of the remaining magnets, characterized in that gaps are respectively formed between the thin portions of the four magnets and the arc-shaped inner faces of the motor case, and gaps are respectively formed between the thin portions of the four magnets and the flat inner faces of the motor case. a motor case (21; 121; 221) formed into a bottomed cylindrical shape; four magnets (22; 122; 222) each formed into an approximately arc shape in cross section; a rotator (23; 123; 223) rotatably provided in an internal space formed by the four magnets; an armature shaft (24; 124; 224) axially aligned with the rotator and fixed to the rotator; and a commutator (25; 125; 225) fixed to an approximately central portion of the armature shaft along an axial direction of the armature shaft, wherein the motor case has a side wall portion to which the four magnets are attached, the side wall portion being composed of a pair of arc-shaped portions (121a; 221a) and a pair of straight portions (121b; 221b), the straight portions intervening between the arc-shaped portions, the four magnets are respectively arranged in the vicinity of four corners between the arc-shaped portions and the straight portions, each of the four magnets has a thick portion and two thin portions smaller in thickness than the thick portion, the thin portions being integrally formed on both sides of the thick portion in the circumferential direction of the motor case, wherein the arc-shaped portions and the straight portions are respectively formed so as to extend from an opening portion side of the motor case to a bottom portion side thereof, the straight portions respectively have flat inner faces parallel to each other, the arc-shaped portions respectively have arc-shaped inner faces, the arc-shaped inner faces being arranged so as to sandwich and face the armature shaft, and the arc-shaped inner faces and the flat inner faces respectively extend along the axial direction of the armature shaft, in a diametrical direction of the armature shaft, one of the flat inner faces is partially overlapped with parts of two magnets, and the other of the flat inner faces is partially overlapped with parts of the remaining magnets, characterized in that gaps are respectively formed between the thin portions of the four magnets and the arc-shaped inner faces of the motor case, and gaps are respectively formed between the thin portions of the four magnets and the flat inner faces of the motor case.