A guidewire catheter includes: a sheath for passing a guidewire therethrough; an operation section connected to an end of the sheath and having a through-hole for passing the guidewire therethrough; a guidewire adapter connected to the operation section and capable of freely extending or retracting relative to the operation section along the axial line of the through-hole, the guidewire adapter grasping the outer periphery surface of the guidewire projecting from the through-hole, and the guidewire adapter being capable of guiding and moving the guidewire relative to the operation section in an axial direction and a circumferential direction of the through-hole; a bar-shaped slide section formed on one of the operation section and the guidewire adapter in the exterior of the through-hole, the slide section being disposed along a line which is parallel with the axial line of the through-hole; a receiver formed on the other one of the operation section and the guidewire adapter and being capable of moving and supporting the freely extendable or retractable slide section; a connection section having a second through-hole formed coaxially with the axial line of the through-hole formed in the guidewire adapter; and a grip section, engaged with the second through-hole, for grasping an outer periphery surface of the guidewire, and the grip section being capable of freely rotatable around the axial line of the second through-hole.