Abstract: A continuous administration device configured to be indwelled in a living body for sustained release of a substance to be administered, the continuous administration device including: a cylindrical main body portion having an inner cavity; a plug slidable in the inner cavity in a liquid-tight manner; a pressing portion disposed on an upstream side with respect to the plug and configured to press the plug toward a downstream side; the substance to be administered, which is stored in the inner cavity on the downstream side with respect to the plug and released into the living body by the plug sliding toward the downstream side; and a sliding solid coating layer that reduces initial sliding resistance and normal sliding resistance of the plug, on at least one of an outer surface of the plug or a region where the plug slides in the inner cavity.