A three-dimensional deposition device for forming a three-dimensional shape by depositing a formed layer on a base unit, comprising: a powder supply unit which supplies a powder material; a light irradiation unit which irradiates the powder material with a light beam in a space between the base unit and the powder supply unit, so that forms a molten body with droplet state by sintering or melting at least a part of the powder material irradiated with the light beam-in the space, and forms the formed layer by solidifying the molten body dropped from the space to the base unit; a heating unit which selectively heats an area having passed through a position irradiated with the light beam in the base unit or the formed layer or an area not having passed through the position irradiated with the light beam; and a control device which controls operations of the powder supply unit, the light irradiation unit, and the heating unit, characterized by comprising a switching mechanism which switches relative positions of the light irradiation unit and the heating unit, wherein, the switching mechanism is configured to switch an upstream relative position and a downstream relative position, the upstream relative position is a state where the light irradiation unit is located at an upstream position of the heating unit in a relative movement directions of the light irradiation unit and the heating unit with the base unit, and the downstream relative position is a state where the light irradiation unit is located at a downstream position of the heating unit in the relative movement directions of the light irradiation unit and the heating unit with the base unit, the control device is configured to detect the relative movement directions of the irradiating unit and the base unit and to specify a heating area; the heating area is an area heating the base unit or the formed layer on which the light irradiation unit has not passed yet, or an area heating the base unit or the formed layer on which the light irradiation unit has already passed; the control device is also configured to determine whether the heating unit is at a position at which the heating area can be heated based on the relative movement directions of the light irradiation unit and the base unit, the heating area, an the current position of the light irradiation unit and the heating unit; the control device is configured to switch the relative positions of the heating unit and the light irradiation unit by the switching mechanism when the control device determines that the heating unit is not located at the position at which the heating area can be heated. a powder supply unit which supplies a powder material; a light irradiation unit which irradiates the powder material with a light beam in a space between the base unit and the powder supply unit, so that forms a molten body with droplet state by sintering or melting at least a part of the powder material irradiated with the light beam-in the space, and forms the formed layer by solidifying the molten body dropped from the space to the base unit; a heating unit which selectively heats an area having passed through a position irradiated with the light beam in the base unit or the formed layer or an area not having passed through the position irradiated with the light beam; and a control device which controls operations of the powder supply unit, the light irradiation unit, and the heating unit, characterized by comprising a switching mechanism which switches relative positions of the light irradiation unit and the heating unit, wherein, the switching mechanism is configured to switch an upstream relative position and a downstream relative position, the upstream relative position is a state where the light irradiation unit is located at an upstream position of the heating unit in a relative movement directions of the light irradiation unit and the heating unit with the base unit, and the downstream relative position is a state where the light irradiation unit is located at a downstream position of the heating unit in the relative movement directions of the light irradiation unit and the heating unit with the base unit, the control device is configured to detect the relative movement directions of the irradiating unit and the base unit and to specify a heating area; the heating area is an area heating the base unit or the formed layer on which the light irradiation unit has not passed yet, or an area heating the base unit or the formed layer on which the light irradiation unit has already passed; the control device is also configured to determine whether the heating unit is at a position at which the heating area can be heated based on the relative movement directions of the light irradiation unit and the base unit, the heating area, an the current position of the light irradiation unit and the heating unit; the control device is configured to switch the relative positions of the heating unit and the light irradiation unit by the switching mechanism when the control device determines that the heating unit is not located at the position at which the heating area can be heated.