A catheter retaining tool comprises a piercing tool, a guide wire and an operation device. The piercing tool includes a Y-hub, an outer needle, an indwelling needle and a syringe. The Y-hub includes a main port, an obliquely connected side port, and a hemostatic valve for keeping the side port liquid-tight. The guide wire is inserted by the operation device from the side port through the hemostatic valve into the outer needle. The operation device includes a turning portion made rotatable relative to the side port and having a hollow portion, an extending portion connected to the turning portion, and a slide portion for pushing out the guide wire along the extending portion. The turning portion includes a first rolling spindle and a second tilting spindle.
