A crossbow includes a body, a grip portion, an aim device rack, a stock connected to the rear end of the body, and two support devices connected to two sides of the front end of the body. Each support device includes an inclined face including a low end is located corresponding to the aim device rack, and a high end located corresponding to the grip portion. A link is connected between the two support devices. A base is connected to the link. Two support legs angularly extend from the base. The crossbow can be operated in a prone position. The crossbow can be positioned between a first position where the two high ends contact the ground, and a second position where both of the high end and the low end of each of the two inclined faces contact the ground. The crossbow does not fall in first and second positions.