An amplifier circuit for a physical random number generator for amplifying a very small signal to generate a physical random number signal includes a pair of first differential input terminals including a first non-inverted input terminal TVin1+ and a first inverted input terminal TVin1−, a pair of second differential input terminals including a second non-inverted input terminal TVin2+ and a second inverted input terminal TVin2−, a differential amplifying section for receiving signals respectively from said pairs of first and second differential input terminals and for producing differential output signals in a form of a linear combination of the input signals, and a first pair of differential output terminals including a first inverted output terminal TVO− and a first non-inverted output terminal TVO+ to output the differential output signals. This configuration increases performance of the amplifier circuit for a physical random number generator.