A method and apparatus for providing a video-on-demand (VOD) service are provided. The VOD service providing method includes: receiving a media setup request message from a user terminal, converting the media setup request message using a second protocol which is different from a first protocol on which the media setup request message is based, transmitting the converted media setup request message through a transmission network, receiving a response message in response to the converted media setup request message through the transmission network, converting the response message using the first protocol on which the media setup request message is based, and transmitting the response message to the user terminal; and converting the converted media setup request message received through the transmission network using the first protocol on which the media setup request message is based, transmitting the newly converted media setup request message to a VOD streaming server, converting the response message from the VOD streaming server using the second protocol, and transmitting the converted response message through the transmission network. Therefore, by preventing overlap of control processes, which may both be initiated when two protocols are used together, it is possible to efficiently perform controlling of a VOD service.