A treadmill comprising: a track unit; a support apparatus rotatably supporting the track unit; and an inclination adjustment apparatus configured to adjust an inclination of the track unit, wherein the inclination adjustment apparatus includes a length adjustment module of which a length is adjustable and is configured to vary an inclination angle of the track unit with respect to a floor as the length thereof is adjusted, the length adjustment module includes: a driving motor a first length adjustment member of which a length is adjustable by a driving force of the driving motor; a connection belt partially wound around the first length adjustment member and a second length adjustment member arranged in parallel to the first length adjustment member, connected to the first length adjustment member by the connection belt, and having a length that is adjustable by the driving force received from the driving motor through the first length adjustment member and the connection belt, characterized in that the connection belt includes: a first curved section wound around the first length adjustment member; a second curved section wound around the second length adjustment member; a first linear section connecting one end portion of the first curved section to one end portion of the second curved section; and a second linear section connecting another end portion of the first curved section to another end portion of the second curved section and corresponding to the first linear section. a track unit; a support apparatus rotatably supporting the track unit; and an inclination adjustment apparatus configured to adjust an inclination of the track unit, wherein the inclination adjustment apparatus includes a length adjustment module of which a length is adjustable and is configured to vary an inclination angle of the track unit with respect to a floor as the length thereof is adjusted, the length adjustment module includes: a driving motor a first length adjustment member of which a length is adjustable by a driving force of the driving motor; a connection belt partially wound around the first length adjustment member and a second length adjustment member arranged in parallel to the first length adjustment member, connected to the first length adjustment member by the connection belt, and having a length that is adjustable by the driving force received from the driving motor through the first length adjustment member and the connection belt, characterized in that the connection belt includes: a first curved section wound around the first length adjustment member; a second curved section wound around the second length adjustment member; a first linear section connecting one end portion of the first curved section to one end portion of the second curved section; and a second linear section connecting another end portion of the first curved section to another end portion of the second curved section and corresponding to the first linear section. a driving motor a first length adjustment member of which a length is adjustable by a driving force of the driving motor; a connection belt partially wound around the first length adjustment member and a second length adjustment member arranged in parallel to the first length adjustment member, connected to the first length adjustment member by the connection belt, and having a length that is adjustable by the driving force received from the driving motor through the first length adjustment member and the connection belt, characterized in that the connection belt includes: a first curved section wound around the first length adjustment member; a second curved section wound around the second length adjustment member; a first linear section connecting one end portion of the first curved section to one end portion of the second curved section; and a second linear section connecting another end portion of the first curved section to another end portion of the second curved section and corresponding to the first linear section.