This paper describes a micro electrical discharge machining (MEDM) technique that uses an insulated tool in combination with ultrasonic vibration to drill micro holes. As the machining depth becomes deeper, the dispersion of debris and circulation of the dielectric fluid are difficult to occur. Consequently, machining becomes unstable in the machining region and unnecessary electrochemical dissolution and secondary discharge sparking occur at the tool side face. To reduce the amount of unnecessary side machining, an insulated tool was used. Ultrasonic vibration was applied to the MEDM work fluid to better remove debris. Through these methods, a $1000;{mu}m$ thick stainless steel plate was machined by using a $73;{mu}m$ diameter electrode. The diameters of the hole entrance and exit were $96;{mu}m$ and $88;{mu}m$, respectively. It took only 351s to completely drill one hole.