Three dimensional printer and method for adjusting working coordinate of platform thereof

A three-dimensional (3-D) printer, comprising:

• a platform comprising a carrying surface and a plurality of adjustment points, the adjustment points located on the carrying surface;
• a printing head disposed above the platform, the printing head configured to move along a datum plane and a normal direction of the datum plane;
• and
• a control unit coupled to the platform and the printing head, the control unit controlling the printing head to move from the datum plane toward the platform to be in contact with the adjustment points respectively for obtaining a plane coordinate of each of the adjustment points corresponding to the datum plane and a shortest distance from each of the adjustment points to the datum plane, and obtaining a coordinate offset value of the carrying surface corresponding to the datum plane according to the plane coordinates and the shortest distances, and adjusting a model coordinate of a digital 3-D model information according to the coordinate offset value, such that the control unit moving the printing head according to the adjusted model coordinate to print a 3-D object related to the digital 3-D model information on the carrying surface.