The present invention relates to a fixing device (11) for fixing a tubular catheter (1) which is equipped with a plate-shaped fixing device body (21) and a fixed member (41). The plate-shaped fixing device body (21) possesses retaining parts (22) and a pair of wing pieces (23) that form a catheter retention slot (25). The fixed member (41) can be fitted onto the fixing device body (21) by being slid along the planar direction of the fixing device body (21). When the fixed member (41) is fitted, the retaining parts (22) are compressed by the fixed member (41), thus narrowing the catheter retention slot (25).
