Abstract: To ensure maintenance operations for an architectural structure using a mast climber without any limitation on the stability of a mast and locations where a mast can be erected. A side wall 101 of an architectural structure 100 is fitted with a fixing member 130 at a level higher than the ground 500. The fixing member 130 is fitted with fixture studs 132. A mast 200 is erected on the fixing member 130 with its lower end secured to the fixture studs 132. A climbing work platform 210 that travels up and down the mast 200 is fixed to the mast 200. A worker performs maintenance operations on the climbing work platform 210.