A method of calculating a quantity of light by measuring, by using an adhering force measuring unit (71), the adhering force of an ultraviolet light-curable tape (11 or 21) relying upon the quantity of ultraviolet light with which the ultraviolet light-curable tape is irradiated from an ultraviolet light irradiation unit (61), and calculating, by using a calculation unit, the quantity of ultraviolet light corresponding to a predetermined adhering force, from the measured adhering force of the ultraviolet light-curable tape, and a device therefor. The predetermined adhering force may have been stored in advance in the storage unit or the predetermined adhering force may be determined in advance relying upon at least either one of the kind of the ultraviolet light-curable tape or the elapsed time of the ultraviolet light-curable tape. Then, the quantity of light necessary for the ultraviolet light-curable tape that is used is automatically calculated to avoid a problem caused by an insufficient quantity of light or an excess quantity of light.