The present invention provides a hook member and a card holder which are respectively provided with a novel structure. Even the width of the hook member and/or the holder is set to a small value, deformation which damages the holder function, and/or dropping of members being held, such as card housing, together with the deformation can be prevented. The hook member is provided with the following components: a hook-shaped hook part (21); and a plate-shaped holder part (22) which is provided at inside of the hook part (21) and opens a loading/unloading opening (OP) between the plate-shaped holder part (22) and the hook part (21) through downwards elastic deformation from the position; wherein: at the top end (22b) of the holder part (22), one position which deflects to one direction from the center in a width direction is provided with a projection (25) which is superposed with the inside of the hook part (21) at a preset position. Furthermore the top end (21b) of the hook part (21) is provided with a projection (26) which is adjacent to the projection (25) at a position which even deflects to one direction over the projection (25) of the holder part (22) at a preset position.