A machine tool comprising: a driving apparatus provided on a supporting unit, the driving apparatus having a supporting-side engaging member provided along a moving direction of a moving unit, and a moving-side engaging member provided on the moving unit movably in the moving direction to be engaged with the supporting-side engaging member, wherein the moving unit moves in the moving direction to machine a workpiece in a first moving range in a first use state and in a second moving range different from the first moving range in a second use state, the machine tool further comprising: a moving-side cover provided on the moving unit to cover part of a position of the driving apparatus in the moving direction; characterized by a supporting-side cover provided in a position on a side of the first moving range of an end of the moving-side cover on a side of the second moving range in the moving direction to continuously cover the part of the position of the driving apparatus in the moving direction in cooperation with the moving-side cover in the first use state, the supporting-side cover forming a clearance in the moving direction with respect to the moving-side cover in the second use state; a slide cover mounted on a companion cover slidably in the moving direction to close the clearance when slidably drawn out in the moving direction from the companion cover in the second use state, the companion cover being one of supporting-side cover and the moving-side cover; a first positioning structure which positions the slide cover in a position adapted to the first use state when the slide cover is slid in the moving direction with respect to the companion cover; and a second positioning structure which positions the slide cover in a position adapted to the second use state. a driving apparatus provided on a supporting unit, the driving apparatus having a supporting-side engaging member provided along a moving direction of a moving unit, and a moving-side engaging member provided on the moving unit movably in the moving direction to be engaged with the supporting-side engaging member, wherein the moving unit moves in the moving direction to machine a workpiece in a first moving range in a first use state and in a second moving range different from the first moving range in a second use state, the machine tool further comprising: a moving-side cover provided on the moving unit to cover part of a position of the driving apparatus in the moving direction; characterized by a supporting-side cover provided in a position on a side of the first moving range of an end of the moving-side cover on a side of the second moving range in the moving direction to continuously cover the part of the position of the driving apparatus in the moving direction in cooperation with the moving-side cover in the first use state, the supporting-side cover forming a clearance in the moving direction with respect to the moving-side cover in the second use state; a slide cover mounted on a companion cover slidably in the moving direction to close the clearance when slidably drawn out in the moving direction from the companion cover in the second use state, the companion cover being one of supporting-side cover and the moving-side cover; a first positioning structure which positions the slide cover in a position adapted to the first use state when the slide cover is slid in the moving direction with respect to the companion cover; and a second positioning structure which positions the slide cover in a position adapted to the second use state. a moving-side cover provided on the moving unit to cover part of a position of the driving apparatus in the moving direction; characterized by a supporting-side cover provided in a position on a side of the first moving range of an end of the moving-side cover on a side of the second moving range in the moving direction to continuously cover the part of the position of the driving apparatus in the moving direction in cooperation with the moving-side cover in the first use state, the supporting-side cover forming a clearance in the moving direction with respect to the moving-side cover in the second use state; a slide cover mounted on a companion cover slidably in the moving direction to close the clearance when slidably drawn out in the moving direction from the companion cover in the second use state, the companion cover being one of supporting-side cover and the moving-side cover; a first positioning structure which positions the slide cover in a position adapted to the first use state when the slide cover is slid in the moving direction with respect to the companion cover; and a second positioning structure which positions the slide cover in a position adapted to the second use state.