An abnormality diagnosis apparatus for an internal combustion engine system which comprises: a plurality of cylinders; an accumulator storing compressed air; an air duct connected to the accumulator; a main starting valve disposed in the air duct; a plurality of starting air ducts branched from the air duct downstream of the main starting valve, into the respective cylinders; a plurality of pilot valves connected to the respective starting air ducts, and configured to open to supply the cylinders with compressed air as starting air; a plurality of pilot air ducts connected to the respective pilot valves, and configured to supply compressed air for opening the valves as pilot air; and a starting air control valve connected to the air duct downstream of the main starting valve, and configured to supply pilot air to normal cylinders which should be supplied with starting air, serially via the pilot air ducts, the abnormality diagnosis apparatus comprising: a cylinder-pressure measuring unit configured to measure a cylinder pressure for each of the cylinders; a starting confirming unit configured to confirm whether the internal combustion engine system fails to start; a cylinder-pressure increase confirming unit configured to confirm an increase of the cylinder pressure for each of the plurality of cylinders, on the basis of a pressure measurement result of the cylinder-pressure measuring unit, if the starting confirming unit confirms a failure; a normal-cylinder confirming unit configured to confirm whether the cylinder for which the increase of the cylinder pressure is confirmed by the cylinder-pressure increase confirming unit is a normal cylinder; a pilot-air pressure measuring unit configured to measure a pressure of the pilot air supplied to each of the pilot valves; and a pilot-air pressure increase confirming unit configured to confirm a pressure increase of the pilot air on the basis of a pressure measurement result of the pilot-air pressure measuring unit; and a diagnosing unit configured to diagnose an abnormal location of the internal combustion engine system on the basis of confirmation results of the cylinder-pressure increase confirming unit, the normal-cylinder confirming unit and a confirmation result of the pilot-air pressure increase confirming unit. a plurality of cylinders; an accumulator storing compressed air; an air duct connected to the accumulator; a main starting valve disposed in the air duct; a plurality of starting air ducts branched from the air duct downstream of the main starting valve, into the respective cylinders; a plurality of pilot valves connected to the respective starting air ducts, and configured to open to supply the cylinders with compressed air as starting air; a plurality of pilot air ducts connected to the respective pilot valves, and configured to supply compressed air for opening the valves as pilot air; and a starting air control valve connected to the air duct downstream of the main starting valve, and configured to supply pilot air to normal cylinders which should be supplied with starting air, serially via the pilot air ducts, the abnormality diagnosis apparatus comprising: a cylinder-pressure measuring unit configured to measure a cylinder pressure for each of the cylinders; a starting confirming unit configured to confirm whether the internal combustion engine system fails to start; a cylinder-pressure increase confirming unit configured to confirm an increase of the cylinder pressure for each of the plurality of cylinders, on the basis of a pressure measurement result of the cylinder-pressure measuring unit, if the starting confirming unit confirms a failure; a normal-cylinder confirming unit configured to confirm whether the cylinder for which the increase of the cylinder pressure is confirmed by the cylinder-pressure increase confirming unit is a normal cylinder; a pilot-air pressure measuring unit configured to measure a pressure of the pilot air supplied to each of the pilot valves; and a pilot-air pressure increase confirming unit configured to confirm a pressure increase of the pilot air on the basis of a pressure measurement result of the pilot-air pressure measuring unit; and a cylinder-pressure measuring unit configured to measure a cylinder pressure for each of the cylinders; a starting confirming unit configured to confirm whether the internal combustion engine system fails to start; a cylinder-pressure increase confirming unit configured to confirm an increase of the cylinder pressure for each of the plurality of cylinders, on the basis of a pressure measurement result of the cylinder-pressure measuring unit, if the starting confirming unit confirms a failure; a normal-cylinder confirming unit configured to confirm whether the cylinder for which the increase of the cylinder pressure is confirmed by the cylinder-pressure increase confirming unit is a normal cylinder; a pilot-air pressure measuring unit configured to measure a pressure of the pilot air supplied to each of the pilot valves; and a pilot-air pressure increase confirming unit configured to confirm a pressure increase of the pilot air on the basis of a pressure measurement result of the pilot-air pressure measuring unit; and a diagnosing unit configured to diagnose an abnormal location of the internal combustion engine system on the basis of confirmation results of the cylinder-pressure increase confirming unit, the normal-cylinder confirming unit and a confirmation result of the pilot-air pressure increase confirming unit.