Abstract: Provided is a mouth shape synthesis device and a method using an artificial neural network. To this end, an original video encoder that encodes original video data which is a target of a mouth shape synthesis as a video including a face of a synthesis target; an audio encoder that encodes audio data that is a basis for the mouth shape synthesis and outputs an audio embedding vector; and a synthesized video decoder that uses the original video embedding vector and the audio embedding vector as input data, and outputs synthesized video data in which a mouth shape corresponding to the audio data is synthesized on the synthesis target face may be provided.