To make frost accurately detectable at a low cost by using an already existing sensor, etc., without using any sensor exclusively used for frost detection.

This cold storage shed is provided with a first frost detecting means which integrates the door opening time of the door 2 of the main body 1 of this shed when the temperature Tf of a storage medium detected by means of a storage medium temperature detecting means 28 is lower than a prescribed value, and estimates the quantity of frost adhering to a cold storage tank 14 based on the integrated opened duration of the door 2. By paying attention to the relative relation between the opened duration of the door 2 and the progress of frost o the cold storage tank 14, the door opening time of the door 2 is integrated and frost detection is performed by estimating the quantity of the frost adhering to the tank 14 based on the integrated opened duration.