Provided is a catheter of which the inner diameter is significant relative to the outer diameter and in which crossability of a medical instrument with respect to a lumen of the catheter can be favorably ensured even in a case where a kink occurs.A catheter (1) includes an inner layer (22) that forms the inner surface of a catheter main body (2) having a lumen (21), an outer layer (23) that forms the outer surface of the catheter main body (2), and multiple reinforcements (25) that are embedded between the inner surface and the outer surface. When the inner diameter of the catheter main body (2) is (D1), the outer diameter is (D2), the wall thickness is (T1), the thickness of each reinforcement (25) along a radial direction of the catheter main body (2) is (T2), the effective width of each reinforcement (25) along the circumferential direction of the catheter main body (2) in a cross section orthogonal to the axial line direction of the catheter main body (2) is (W), and the number the reinforcements (25) is (N), Expressions (1), (2), and (3) below are satisfied 0.050mm≤T1≤0.100mmT2/T1≥0.2560,000≤D1×D2×W×N/T1
