Additive manufacturing apparatus and method of producing three-dimensionally shaped object

A method of producing a three-dimensionally shaped object, the method comprising:

• a step of equipping an additive manufacturing apparatus with a plate;
• a step of forming a support portion comprising multiple layers by repetitively depositing raw material powder on the plate and radiating light;
• and
• a step of forming a first layer of the three-dimensionally shaped object by depositing raw material powder on the support portion and radiating light,
• wherein, in the step of forming the support portion, a low-density support portion and a high-density support portion are formed adjacently in each layer of the multiple layers, the low-density support portion having a lower density than the first layer of the three-dimensionally shaped object, and the high-density support portion having a higher density than the low-density support portion, and
• wherein an area in which the high-density support portion is in contact with the three-dimensionally shaped object is smaller than an area in which the high-density support portion is in contact with the plate.