1. A 3D printer having manual flat scanner, comprising: a device body ( 100 ) on which a printing plane ( 101 ) is defined; and a scanning module ( 200 ) arranged on the device body ( 100 ), wherein the scanning module ( 200 ) is electrically connected with a control module ( 300 ) which is electrically connected with a nozzle assembly ( 310 ) and a pen assembly ( 320 ), wherein a 3D data is loaded in the control module ( 300 ) and a predetermined painting position is defined in the 3D data, wherein the control module ( 300 ) receives a scan image from the scanning module ( 200 ) and controls the nozzle assembly ( 310 ) to print a model ( 20 ) according to the 3D data and meanwhile the control module ( 300 ) controls the pen assembly ( 320 ) to paint on the model ( 20 ) according to the predetermined painting position and the scan image during the printing of the model ( 20 ); wherein the scanning module ( 200 ) comprises a module body ( 210 ), a closure mechanism ( 220 ), and a flat scanner ( 230 ), wherein the module body ( 210 ) has a feeding channel ( 201 ) disposed corresponding to a side edge of the printing plane ( 101 ), wherein the closure mechanism ( 220 ) closes the feeding channel ( 201 ) selectively, wherein the flat scanner ( 230 ) is disposed in the feeding channel ( 201 ) correspondingly; wherein the module body ( 210 ) comprises a base ( 211 ) and a movable cover ( 212 ) stacked above the base ( 211 ), wherein the closure mechanism ( 220 ) is connected between the base ( 211 ) and the movable cover ( 212 ); wherein the closure mechanism ( 220 ) is a rebound device.