A refrigerating cycle wherein the pressure of a high pressure line (8) is lowered when the pressure is abnormally high by transmitting the high pressure to the low pressure line (9) without releasing the coolant to the atmosphere, and the coolant is released to the atmosphere only when the pressure of the low pressure line (9) is abnormally high. First safety means (10) for communication of the high pressure line (8) with the low pressure line (9) is provided, and second safety means (11) is provided between the low pressure line (9) and the atmosphere. The high pressure coolant of the high pressure line (8) is leaked to the low pressure side by the first safety means (10) when the high pressure exceeds a first pressure. Hence, the pressure rise of the high pressure line (8) can be lessened by the allowance of the low pressure line (9), and the high pressure is lowered to prevent the outflow of the coolant. Only when the pressure of the low pressure line (9) exceeds a second pressure, the coolant is released to the atmosphere by the second safety means, so that release of the coolant of the refrigerating cycle can be avoided as much as possible.