A subscriber-side optical communication device that includes an optical transmission-and-reception module arranged to perform transmission and reception of a signal with a station-side optical communication device and is configured to cause a receiver and a transmitter constituting the optical transmission-and-reception module to enter into a power-saving state separately, the subscriber-side optical communication device comprising: a clock regeneration unit arranged to regenerate a clock based on a signal from the station-side optical communication device received by the optical transmission-and-reception module and to supply the clock; an internal clock source arranged to generate an internal clock and supplies the internal clock; a time management unit (209; 219) arranged to manage a time of the subscriber-side optical communication device based on the clock in a period in which the clock regeneration unit supplies the clock and manages the time of the subscriber-side optical communication device based on the internal clock in a period in which the clock regeneration unit does not supply the clock; characterized by a sleep-time control unit (208; 211) arranged to decide, when a power-saving mode for causing the receiver to enter into a power-saving state for a predetermined sleep time is set, a receiver-time synchronization time that is a period in which the receiver is normally operated within the sleep time, based on a difference between predetermined information indicating a time in the station-side optical communication device included in the signal transmitted from the station-side optical communication device and the time managed by the time management unit (209; 219); and a power-saving control unit arranged to control the receiver to be normally operated in the receiver-time synchronization time during the sleep time. a clock regeneration unit arranged to regenerate a clock based on a signal from the station-side optical communication device received by the optical transmission-and-reception module and to supply the clock; an internal clock source arranged to generate an internal clock and supplies the internal clock; a time management unit (209; 219) arranged to manage a time of the subscriber-side optical communication device based on the clock in a period in which the clock regeneration unit supplies the clock and manages the time of the subscriber-side optical communication device based on the internal clock in a period in which the clock regeneration unit does not supply the clock; characterized by a sleep-time control unit (208; 211) arranged to decide, when a power-saving mode for causing the receiver to enter into a power-saving state for a predetermined sleep time is set, a receiver-time synchronization time that is a period in which the receiver is normally operated within the sleep time, based on a difference between predetermined information indicating a time in the station-side optical communication device included in the signal transmitted from the station-side optical communication device and the time managed by the time management unit (209; 219); and a power-saving control unit arranged to control the receiver to be normally operated in the receiver-time synchronization time during the sleep time.