A plasticizing device includes: a drive motor; a rotating unit driven to rotate about a rotation axis by the drive motor and having an end surface perpendicular to the rotation axis and a lateral surface intersecting with the end surface; a barrel having a bottom surface facing the end surface of the rotating unit, and a heater; a case accommodating the rotating unit; and a material supply unit accommodating the material. At least one of the barrel and the case has a sidewall surface facing the lateral surface of the rotating unit and standing up along an outer circumference of the bottom surface of the barrel. At the bottom surface of the barrel, a communication hole through which the molten material flows out and a spiral groove part coupled to the communication hole are formed. The lateral surface of the rotating unit and the sidewall surface together define a supply space where the material is supplied from the material supply unit to the groove part.