According to an embodiment, a detection system detects deterioration of a rope through at least one sheave. The system includes a plurality of sensors and a calculator. The sensors are configured to detect an elastic wave generated from the rope and convert the elastic wave into a detection signal. At least one of the sensors is installed near an end portion of the rope. At least one of the sensors is installed at the sheave. The calculator is configured to calculate a position of the rope where the elastic wave has been generated, based on a propagating speed of the elastic wave, time difference information of a plurality of detected times of the elastic waves detected by the respective sensors, and positional information indicating positions of the respective sensors.