Provided are an audio encoding method and apparatus and an audio decoding method and apparatus in which audio signals can be encoded or decoded so that sound images can be localized at any desired position for each object audio signal. The audio decoding method includes extracting a downmix signal and object-based side information from an audio signal; generating channel-based side information based on object-based side information and control information for rendering the downmix signal; processing the downmix signal using a decorrelated channel signal; and generating a multi-channel audio signal using the processed downmix signal and the channel-based side information.