PROBLEM TO BE SOLVED: To provide a light irradiation device in which temperature rise of inside air of a photocurable lining material, the photocurable lining material itself, and respective components of the light irradiation device at a light irradiation time can be suppressed; and an existing tube maintenance method using the same.SOLUTION: A mobile type light irradiation device 10 is that in a condition in which in an inside of a tubular photocurable lining material introduced in an existing tube, a gas is sent from one end to the other end thereof, the photocurable lining material is performed by light irradiation from an inside thereof, and the light irradiation device 10 is characterized by including gas current change means 32-1-4 that change a current of the gas being sent without separately introducing a gas in the inside of the photocurable lining material.
