The present invention is a catheter device provided with a catheter (2) and a sheath (1) through which the catheter passes. The catheter has an insertion guide member (5) attached to its tip, a balloon (3) provided on the tip side for widening the diameter of a vascular stent (4), and an expansion medium supply path (7) through which the expansion medium for expanding the balloon is supplied. The sheath is operated to move, relative to the catheter, over a span between a position where the sheath covers the balloon to which the vascular stent is fitted and a position where the vascular stent fitted onto the balloon is at the verge of being outside the sheath. The following are provided between the sheath and the catheter: a first movement restriction part (35) that regulates the projection of the tip-side of the sheath from the tip-side of the catheter, and a second movement restriction part (40) that regulates the amount that the tip-side of the catheter projects outward. By regulating the relative movement position of the sheath with respect to the catheter, excess movement of the sheath is controlled.
