To accurately detect a trouble of a magnetic brake (2) by eliminating any effect of a temperature of a location at which an elevator is installed, a temperature sensor (3) is arranged to measure a temperature of the magnetic brake (2). When an armature (2c) has been attracted responsive to a brake release command, the temperature of the magnetic brake is measured as a first temperature, and before the armature returns responsive to a brake actuation command, the temperature of the magnetic brake is measured as a second temperature. The first and second temperatures are compared with each other. When a result of the comparison between the first and second temperatures is determined to be greater than a predetermined value, the magnetic brake (2) is determined to have been locked and hence, to have developed a trouble.