A physical quantity sensor for detecting a physical quantity includes: a first substrate having a first physical quantity detection element; a second substrate having a second physical quantity detection element, wherein the second substrate contacts the first substrate; and an accommodation space disposed between the first substrate and the second substrate. The first physical quantity detection element is disposed in the accommodation space. The first physical quantity detection element is protected with the first substrate and the second substrate since the first physical quantity detection element is sealed in the accommodation space.