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, and a needle support portion for supporting the inner needle through the catheter on a leading end side beyond the catheter hub, wherein 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 support arms in a closed state and releasing a restraint of the pair of support arms, the needle hub having an extension portion extending in a leading end direction beyond the catheter hub, the pair of support arms being laterally disposed between the restraining portion.