The sand moulding machine (1) includes a moulding chamber (2) formed by a chamber top wall (3), a chamber bottom wall (4), two opposed chamber side walls and two opposed chamber end walls (7, 8). A chamber wall is provided with a sand filling opening (9) communicating with a sand feed system (10). At least one of the chamber end walls is provided with a pattern plate (12, 13) having a pattern (14, 15). At least one of the chamber end walls is displaceable in order to compact sand fed into the moulding chamber. A number of compressed air inlet openings (18, 43) are located in a lower part of the moulding chamber and are arranged to form an upward airflow in at least a part of the moulding chamber in order to create an at least substantially fluidised bed of sand during a sand filling operation.