Disclosed is a temporary device for a building used in case of rain. A temporary device for a building used in case of rain according to one embodiment of the present invention includes: a cover unit with a diameter change unit mounted in a circumferential direction to change the diameter corresponding to the diameter of an upper opening of a building under construction in a nuclear power plant; and a connecting unit enabling the movement of the cover unit by being positioned to be separated from the top of the cover unit by a medium of a connection member and being selectively connected to heavy equipment.
