PURPOSE: To shorten a construction term by replacing an existing door on landing side at each story with a new one, attaching an existing engaging piece on landing side to a newly installed door, replacing a door opening and closing device on car side, and engaging an engaging piece of a door on landing side at each story with a new door on car side.

CONSTITUTION: Existing doors 50-1 to 50-N on landing side of an elevator at each story are replaced with new doors 60-1 to 60-N sequentially. Existing engaging pieces 61-1 to 61-N at each story are engageable with an existing opening and closing device 51 on car side. Then, a door on car side and the opening and closing device 51 are replaced with a new one 62. Next, engaging elements 61-1 to 61-N on landing side are adjusted so as to engage them with the newly installed car door opening and closing device 62 or are replaced with new ones as required. Consequently, operation impossible time in sections other than the elevator during construction is shortened, and service is improved.