An arrow shaft pressing device for a crossbow includes a sleeve connected to one end of the aiming device and has a passage with an aperture defined through the lower end of the sleeve. A shoulder is formed at the connection portion between the passage and the aperture. A pressing member has a flange and a shank extending from the underside of the flange. The pressing member is located in the passage of the sleeve and the distal end of the shank extends beyond the aperture. A restriction member is connected to the top end of the sleeve. A resilient member is biased between the flange of the pressing member and the restriction member. The distal end of the shank of the pressing member resiliently presses the arrow shaft.