A printing apparatus comprising: a plurality of plate cylinders for printing different colors; arranged in a circumferential direction at predetermined intervals in a state where the centers of the plate cylinders are located on the circumference of a circle whose center is located at the center of a blanket cylinder, a plurality of ink supply units which respectively supply ink to the plate cylinders; a machine frame which supports the plurality of plate cylinders and the plurality of ink supply units, an ink supply unit moving device which moves the ink supply unit between the operation position and the standby position the ink supply unit being in contact with a respective plate cylinder when at the operating position, and the ink supply unit being out of contact with the respective plate cylinder when at the standby position, wherein the ink supply unit is a unitized member having a casing accommodating components therein, wherein each ink supply unit corresponding to the plate cylinder is disposed on a radially outer side of the plate cylinder, and wherein the ink supply unit moving device moves the casing of the ink supply unit to move the ink supply unit between the operation position in which ink can be supplied to the plate cylinder and the standby position located further to an outer side in a radial direction of the blanket cylinder than the operation position wherein, when the ink supply unit is located at the standby position, a first gap is provided between the ink supply unit and the respective plate cylinder and a second gap is provided between the ink supply unit and adjacent ink supply units so that maintenance can be performed on the ink supply unit or the respective plate cylinder and wherein, when the ink supply unit is located at the operation position a significantly smaller gap than the second gap is provided between the ink supply unit and the adjacent ink supply units. a plurality of plate cylinders for printing different colors; arranged in a circumferential direction at predetermined intervals in a state where the centers of the plate cylinders are located on the circumference of a circle whose center is located at the center of a blanket cylinder, a plurality of ink supply units which respectively supply ink to the plate cylinders; a machine frame which supports the plurality of plate cylinders and the plurality of ink supply units, an ink supply unit moving device which moves the ink supply unit between the operation position and the standby position the ink supply unit being in contact with a respective plate cylinder when at the operating position, and the ink supply unit being out of contact with the respective plate cylinder when at the standby position, wherein the ink supply unit is a unitized member having a casing accommodating components therein, wherein each ink supply unit corresponding to the plate cylinder is disposed on a radially outer side of the plate cylinder, and wherein the ink supply unit moving device moves the casing of the ink supply unit to move the ink supply unit between the operation position in which ink can be supplied to the plate cylinder and the standby position located further to an outer side in a radial direction of the blanket cylinder than the operation position wherein, when the ink supply unit is located at the standby position, a first gap is provided between the ink supply unit and the respective plate cylinder and a second gap is provided between the ink supply unit and adjacent ink supply units so that maintenance can be performed on the ink supply unit or the respective plate cylinder and wherein, when the ink supply unit is located at the operation position a significantly smaller gap than the second gap is provided between the ink supply unit and the adjacent ink supply units.