Provided is a drug supply unit for supplying a drug of solid form, the unit being provided with: a drug supply body having a drug accommodation part for accommodating a drug, and a driven shaft part rotatable with respect to the drug accommodation part, the drug being supplied from the drug accommodation part by driving the rotation of the driven shaft part and a support body which detachably supports the drug supply body, and which has a rotation driving source, and a drive shaft part to which the driven shaft part connects coaxially and which is driven to rotate by the rotation driving source. The driven shaft part has a driven shaft part body, and a driven engagement member moveable in the axial direction with respect to the driven shaft part body. The drive shaft part has a drive shaft part body, and a driving engagement member fastened to the drive shaft part body, and engaging the driven engagement member. The driven engagement member is further provided with a rotation inhibiting part which is energized in an approaching direction to approach the drive engagement member, and which in the installed state with the drug supply body installed on the support body, permits rotation of the driven engagement member in the engaged state when the driven engagement member and the drive engagement member are engaged, and inhibits rotation of the driven engagement member in the abutting state in which the driven engagement member and the drive engagement member are abutting without being engaged.
