The invention discloses an electro-deposition device with an electrode machining gap adaptively adjusted and a working method thereof. An electrode holder is fixed above a working cavity; a tool electrode is suspended in an electrode holder inner hole through a spring; a workpiece is installed on a workbench at the lower end of the tool electrode; and the workbench controls automatic feeding along the Z axle through an upper contact and a lower contact. An electrolyte solution flows into a tool electrode inner hole through the electrode holder and is sprayed to the workpiece to generate counter-acting force, the tool electrode adaptively and upwards moves, a diversion hole in the tool electrode is gradually shielded by the electrode holder, the flow of the tool electrode inner hole is increased, so that the flowing speed of water flow is increased on the condition that the machining gap is not changed, then the percussion counter-acting force of the water flow is enlarged so as to counteract changes of the machining gap caused by changes of elasticity of the spring, and stability for balancing the machining gap is maintained. When the deposition thickness reaches a certain height, the lower contact arranged at the top end of the tool electrode makes contact with the upper contact at the top end of the electrode holder, a feeding loop of the workbench is connected, the workbench feeds downwards, and automatic machining is achieved.