To provide an audio system for a vehicle wherein an occupant can sufficiently enjoy music on both inside and outside of a cabin.

The audio system determines whether or not an automatic rear door is in an opened state (step S1), and outputs four divided sound signals to speakers on front and rear parts in the cabin (step 2) when the automatic rear door is in a full-closed state (NO in step S1). When the automatic rear door is in an opened state (YES in step 1), the speaker on the rear part in the cabin is directed to a rearward of a vehicle body (S3). When the automatic rear door is in the full-closed state, while the divided sound signal to be outputted to a right speaker on the front part in the cabin is outputted to a right speaker on the rear part in the cabin, the divided sound signal to be outputted to a left speaker on the front part in the cabin is outputted to a left speaker on the rear part in the cabin, and while the divided sound signal to be outputted to the right speaker on the rear part in the cabin is outputted to a right speaker of the rear door, and the divided sound signal to be outputted to the left speaker on the rear part in the cabin is outputted to a left speaker of the rear door (step S4).