A catheter assembly is disclosed, which includes a catheter； a catheter hub fixed to a base end portion of the catheter； an inner needle having a needlepoint, inserted into the catheter； a needle hub coupled to the inner needle； a needle support portion configured to support the inner needle through the catheter on a leading end side beyond the catheter hub, the needle support portion having a pair of support arms openable and closeable in a lateral direction； a restraining portion capable of restraining the pair of support arms in a closed state and releasing a restraint of the pair of support arms； and wherein the restraining portion is movable with respect to the pair of support arms by a distal movement of the catheter hub relative to the inner needle, which releases the restraint with respect to the pair of support arms.
