Abstract: A device for inducing sleep according to the present invention comprises: a sensor configured to be wearable on a user's body, and contacting a part of the user's body to obtain a sleep-related signal; an output module that outputs a synthesized sound source obtained by mixing a first sound source for inducing the user's sleep and a second sound source different from the first sound source; and a control unit. The control unit transmits the sleep-related signal to an external device, receives sleep state information of the user according to an analysis of the sleep-related signal from the external device, and adjusts an output ratio of the first and second sound sources constituting the synthesized sound source and outputs the first and second sound sources, on the basis of the received sleep state information of the user. Accordingly, the user can fall asleep more comfortably, sleep soundly, and wake up refreshed.