He didn't go far!

Ben Affleck has swooped up this $20 million Pacific Palisades mansion, and it's conveniently located less than half a mile down the street from his ex Jen Garner!

The actor's new pad comes with seven bedrooms and seven bathrooms, which is the perfect size for him, girlfriend Lindsay Shookus, and all of their combined kiddos. There's also a gym, movie room, wine cellar and guest house.

The Batman star and his SNL producer lady love shaking up is just the latest evidence that they're serious.

A source tells X17:
    "It was important for Ben that Lindsay felt included in the decision about which house to buy. He told her that he wanted plenty of rooms, so that all three of his kids could have their own, and her daughter could also have her own when she comes to California and stays with them. He's happy to have a home base."

We caught the Oscar winner leaving his place with his brood, and they all seem to already be right at home!