An inter-prediction method and a video encoding/decoding method using the inter-prediction method are disclosed. The video encoding method using inter-prediction includes: encoding a first picture that serves as a reference for random access; inter-prediction encoding a block included in a second picture, which is displayed before the first picture, by using a plurality of reference pictures; generating reference picture information representing whether a past picture, which is displayed before the second picture, is used as a reference picture for encoding the second picture; and transmitting the encoded first and second pictures and the reference picture information.