An artificial bone forming method, comprising a) a powder layer forming step (32) for forming, into a flat powder layer (6), a powder bone material (5) having biocompatibility and hardening by hydration, b) a partial hardening step (34) for jetting an aqueous solution (7) with biocompatibility to a part of the powder layer to harden a jetted portion (6a) by hydration, and c) an artificial bone forming step (36) for repeating the steps a) and b) for lamination to form a specified artificial bone (9) of a predetermined three-dimensional structure in which the hardened portions (6a) are connected to each other.