Plasticizing device, injection molding device, and three-dimensional shaping device

A plasticizing device comprising:

• a motor;
• a flat screw having a groove formation surface in which a spiral groove is formed and configured to rotate about a rotation axis by the motor;
• a barrel having a facing surface facing the groove formation surface in a direction of the rotation axis and having a communication hole into which a plasticized material obtained by plasticizing a material flows;
• a heater configured to heat the material supplied between the groove formation surface and the facing surface;
• and
• a screw case accommodating the flat screw and having a supply port through which the material is supplied to the groove, wherein
• the flat screw includes
• a first side surface in which an introduction port for introducing the material from the supply port into the groove is partially formed, and
• a second side surface provided on a side farther away from the barrel than the first side surface,
• a first distance which is a shortest distance between the first side surface and the screw case is larger than a second distance which is a shortest distance between the second side surface and the screw case, and
• a recessed portion is formed in the second side surface.