A 3D printer to create a 3D object using a powder material and a binder, including: a recoater provided with a length of one side of a printing table and adapted to deposit the powder material on a top surface of the printing table uniformly; an ink jet head adapted to discharge the binder on the deposited powder material on the basis of printing data to create the 3D object; and characterised in that the 3D printer includes Z two parallel recoater rails which are provided parallel to a Y-direction of a side adjoining said one side of the printing table; a mounting bar which is bridged between the two parallel recoater rails and adapted to move along the two parallel recoater rails in the Y-direction, the recoater being attached to the mounting bar; two parallel head rails which are provided in parallel above the two parallel recoater rails; and a first head rail which is bridged between the two parallel head rails and adapted to move in the Y-direction along the two parallel head rails, the ink jet head being attached to the first head rail and being adapted to move in a X-direction of said one side along the first head rail, first offset rails formed by extending the both sides of the two parallel recoater rails which have slant parts formed by bending the extended both side parts of the two parallel recoater rails downward and parallel parts connected to the slant parts which are parallel to the two parallel recoater rails, the recoater being adapted to be positioned at the parallel parts of the first offset rails in a retracted state; and second offset rails formed by extending the both sides of the two parallel head rails which have slant parts formed by bending the extended both side parts of the two parallel head rails upward and parallel parts connected to the slant parts which are parallel to the two parallel head rails, the ink jet head being adapted to be positioned at the parallel parts of the second offset rails in a retracted state, wherein where right in the middle of said recoater moving in a direction perpendicular to said one side and depositing powder material on said printing table, said ink jet head is adapted to follow said recoater to coat binder on the powder material deposited by said recoater. a recoater provided with a length of one side of a printing table and adapted to deposit the powder material on a top surface of the printing table uniformly; an ink jet head adapted to discharge the binder on the deposited powder material on the basis of printing data to create the 3D object; and characterised in that the 3D printer includes Z two parallel recoater rails which are provided parallel to a Y-direction of a side adjoining said one side of the printing table; a mounting bar which is bridged between the two parallel recoater rails and adapted to move along the two parallel recoater rails in the Y-direction, the recoater being attached to the mounting bar; two parallel head rails which are provided in parallel above the two parallel recoater rails; and a first head rail which is bridged between the two parallel head rails and adapted to move in the Y-direction along the two parallel head rails, the ink jet head being attached to the first head rail and being adapted to move in a X-direction of said one side along the first head rail, first offset rails formed by extending the both sides of the two parallel recoater rails which have slant parts formed by bending the extended both side parts of the two parallel recoater rails downward and parallel parts connected to the slant parts which are parallel to the two parallel recoater rails, the recoater being adapted to be positioned at the parallel parts of the first offset rails in a retracted state; and second offset rails formed by extending the both sides of the two parallel head rails which have slant parts formed by bending the extended both side parts of the two parallel head rails upward and parallel parts connected to the slant parts which are parallel to the two parallel head rails, the ink jet head being adapted to be positioned at the parallel parts of the second offset rails in a retracted state, wherein where right in the middle of said recoater moving in a direction perpendicular to said one side and depositing powder material on said printing table, said ink jet head is adapted to follow said recoater to coat binder on the powder material deposited by said recoater.