An optical transmission device which performs relaying between a terminal device and a server via an optical network device, the terminal device and the server establishing connection with each other, includes a request detection unit which detects a connection establishment request transmitted to the server by the optical network device on the basis of a connection establishment request transmitted to the server by the terminal device, a response detection unit which detects an acknowledgment transmitted to the terminal device by the server on the basis of the connection establishment request detected by the request detection unit, and a band allocation unit which, if the response detection unit detects the acknowledgment, performs allocation so as to expand a band over which the optical network device is capable of transmission to the server, regardless of presence or absence of a buffer amount notification to be transmitted by the optical network device.