an acceleration sensor with reduced noise that resolves the problem of stress arising from a difference in thermal expansion coefficients is provided . the acceleration sensor detects acceleration in three - axis directions in a three - dimensional coordinate system , and includes a frame having four sides that is integrally formed by a semiconductor substrate ; a weight portion that is positioned within the frame ; and four beam portions , corresponding with each of the four sides , one end of which is connected to the weight portion to support the weight portion and the other end of which is connected to the center of the corresponding side of the four sides , wherein a detection element that detects flexure of the beam portions that corresponds to the acceleration acting on the weight portion is formed on each of the four beam portions ; a pair of joint portions that are formed with a gap there between are formed on each of the four sides of the frame ; and the gap between the pair of joint portions formed on one side has a predetermined length with the center of the one side as the point of symmetry .