An insulation sheet forming apparatus that forms an insulation sheet having one or more bent regions includes an unwinding module; a preforming module configured to form a preforming region on the insulation sheet supplied from the unwinding module; and a bending module configured to form the bent region on the insulation sheet by bending the insulation sheet supplied from the preforming module, in which the preforming module has a width which is adjustable in a width direction that intersects a movement direction of the insulation sheet.