An automatic inkjet head cleaning method for a powder bed and inkjet 3D printer is provided, and the method includes steps: controlling a powder-laying module and a plurality of the inkjet heads of the powder bed and inkjet 3D printer to print a 3D physical model according to 3D printing data; retrieving a status value continuously or intermittently during printing; executing the first cleaning procedure for cleaning all or parts of the inkjet heads when determining the status value satisfies the first cleaning configuration value; and executing the second cleaning procedure for cleaning all or parts of the inkjet heads when determining the status value satisfies the second cleaning configuration value. The method automatically cleans the inkjet heads during the printing process, which effectively improves printing quality and reduces printing failure rates.