A torsion coil spring has first and second coil parts and first to third straight line parts. One end of the first coil part is continued to a first straight line part, while the other end is continued to one end of a second straight line part. The other end of the second straight line part is continued to one end of a second coil part, and the other end of the second coil part is continued to one end of the third straight line part. Also, a mobile terminal having a first housing slidably coupled to a second housing is provided. On the surface of the second housing, a pair of rail parts is provided extending in a sliding direction of the first housing. Between the rail parts, the torsion coil spring is provided for aiding sliding of the first housing on the rail parts of the second housing.