Strain body and force sensor provided with the strain body

A strain body, comprising:

• a central portion;
• an outer peripheral portion surrounding the central portion;
• connecting portions connecting the central portion and the outer peripheral portion, and each comprising a first connecting portion adjacent to the outer peripheral portion and a second connecting portion adjacent to the central portion;
• strain sensors provided on main surfaces of the connecting portions;
• reference resistors provided on a main surface of the central portion, and constructing a bridge circuit with the strain sensors;
• and
• a strain increasing portion configured to increase strain occurring at the first connecting portion more than strain occurring at the second connecting portion, on a back surface side opposed to the main surface of the first connecting portion.