A detector has first and second excitation beams extending along X-axis and Y-axis directions. These beams are fixed to a substrate via an intersecting portion. Mass portions are disposed at free ends of the beams. Sensing electrodes are disposed at the central portions of the mass portions to face the mass portions. By electrostatic force generated between the excitation electrodes and the mass portions, two mass portions vibrate in the Y-axis direction, while the remaining two mass portions vibrate in the X-axis direction. When an angular velocity .OMEGA..sub.x acts about the X axis, Z-axis Coriolis forces F.sub.1a and F.sub.1b act on the mass portions that are vibrating in the Y-axis direction. When an angular velocity .OMEGA..sub.y acts about the Y axis, Z-axis Coriolis forces F.sub.2a and F.sub.2b act on the mass portions that are vibrating in the X-axis direction. These vibrations are detected by the sensing electrodes in order to detect the angular velocities .OMEGA..sub.x and .OMEGA..sub.y.