A MEMS electromagnetic optical scanner for horizontal scanning in a commercial laser scanning microscope has been developed. Major specifications include mirror size: 4.5 × 3.3 mm2, resonant frequency: 4 kHz, changeable scan angle: 2.1 - 16 °, mirror flatness: <244 nm, and scan angle stability: <0.1 %. Initial development started with prototyping a scanner with polyimide hinge, but the stiffness and the Q-factor of polyimide hinge were found insufficient to realize the required resonant frequency and scan angle. On the other hand, a scanner with single crystal silicon hinge has been successfully developed. The electromagnetic scanner has a copper-electroplated driving coil and an improved magnetic circuit to reduce power consumption. A scanner controller using the output signal from an integrated sensing coil was also developed, and sufficient scan angle stability was obtained. The scanner has survived the life test of over 140 billion cycles. It has successfully satisfied all the specifications including not only the fundamentals such as resonant frequency and maximum scan angle but also the ones for commercial products such as scanning stability and durability. It has been commercialized as a part of our product OLS1100 (remodeled as OLS1200 as of Aug. 2002).