A method for joining an aluminum material includes, in the following order, arranging a first wrought aluminum alloy material along a first jig in an internal space defined between the first jig and a second jig that is arranged to face the first jig and has a pouring port, pouring molten aluminum toward the first wrought aluminum alloy material through the pouring port under pressure to cause the molten aluminum to collide with a surface of the first wrought aluminum alloy material, thereby digging down the first wrought aluminum alloy material at a collision position between the molten aluminum and the first wrought aluminum alloy material, and flowing the molten aluminum together with a fraction of the first wrought aluminum alloy material removed by digging within the internal space along a surface of the first wrought aluminum alloy material around the collision position.