A catheter assembly is disclosed, which includes a needle support portion that supports an inner needle through a catheter on the leading end side beyond a catheter hub. The needle support portion has a pair of support arms openable and closeable in a left and right direction, and a restraining portion capable of restraining the pair of arms in a closed state and releasing the restraint. A needle hub has an extension portion extending in a leading end direction beyond the catheter hub. A coupling portion between each of the pair of support arms and the extension portion is positioned on the leading end side beyond a base end of the catheter hub.
