Abstract: Operational data of an elevator are constantly and successively stored in RAM of a terminal supervisor unit. If the elevator develops a malfunction which lasts for a predetermined time, this malfunction is detected and reported from the terminal supervisor unit to a supervisor center, together with relevant data, such as the place of occurrence of the malfunction, the code number of the elevator in question and the kind of malfunction. The data relevant to the malfunction are collected at a time point when predetermined specific data indicate that a malfunction is likely. For this purpose, malfunction-indicating states of the specific data are preset and stored in a preset value storage unit, for each possible kind of malfunction, and are constantly compared with the corresponding actual data. By collecting relevant data before actual determination of a malfunction, an investigation for a cause of the malfunction through an analysis of data can be performed more accurately.