A stress-detecting element includes a support body, a support film, a first piezoelectric element, first and second elastic parts. The support body has an opening part with first and second rectilinear sections extending parallel to each other. The support film blocks off the opening part. The first piezoelectric element straddles the first rectilinear section from an interior area to an exterior area of the opening part as seen in plan view. The first elastic part straddles the first rectilinear section from the interior area to the exterior area of the opening part. The second elastic part straddles the second rectilinear section from the interior area to the exterior area of the opening part. The first and second elastic parts respectively have first and second elastic end sections disposed in the interior area of the opening part and spaced apart from each other.