A high-gain, low-noise amplifier for microelectrode probe, which integrated multimicroelectrode array for extracellular recording of neural activities and solid state circuits for the amplification of induced signals from the electrodes onto one substrate, was fabricated. In the amplifier, low-noise MOSFETs are used in the first stage, an interstage high-pass filter is incorporated to avoid saturation of the amplifier due to the polarization voltage of the electrode. In the second stage, an operational amplifier incorporating Bi-MOSFETs for the realization of high input impedance and large gain-bandwidth product is used. The gain of the fabricated amplifier is 56 dB for the frequency range between 2 Hz to 10 kHz, the noise voltage is 20µVpp; these satisfied design specifications.