To provide an inexpensive shaft seal device for easily changing a mechanical seal and a bearing provided on a high-speed shaft without drawing out a refrigerant, in a turbo refrigerating machine using a high-pressure refrigerant.

A high-speed shaft 20 is pressed and inserted to a mechanical seal housing 24 side by differential pressure between a refrigerant and the atmosphere by detaching a thrust bearing 28, an O-ring 25 provided between the mechanical seal housing 24 and the high-speed shaft 20 is pressed to seal the high-pressure side and the low-pressure side. Therefore, since this shaft seal device requires no additional parts and functions for satisfying a sealing function, the structure is simple, and material cost and manufacturing cost are low.