A three-dimensional (3D) printer is characterized by comprising an X-axis track frame (1), a Z-axis track frame (2), a Y-axis track frame (3), a universal numerical control steering frame (4), a conductive base plate (5), a coaxial sleeve printing head (6) installed on the universal numerical control steering frame (4), a backflow outer hose (7) connected with an outer tube of the coaxial sleeve printing head (6), an automatic-flowing inner hose (8) connected with an inner tube of the coaxial sleeve printing head (6), a storage tank (9) containing electrolyte, a metal electrode block (10) and a numerical control sucking pump (11) installed at the tail end of the backflow outer hose (7) and used for sucking the electrolyte into the storage tank (9). The metal electrode block (10), a electrolyte solution, the conductive base plate (5) and a direct-current power supply of the 3D printer form an electrolysis device, the electrolyte solution is electrolyzed on the conductive base plate (5), and a precipitated metal coating serves as an accumulation printing material. The shortcoming of lower printing efficiency of a 3D printer in the prior art is overcome, the accumulation printing material is low in price, an etching and accumulation method is simple, and the electrolytic etching electroplating accumulation 3D printer is high in printing speed.