An optical coupling device capable of maintaining anti-noise property and reducing semiconductor chip is provided. The optical coupling device has a light emitting element, first and second photodiodes, first and second inverting amplifiers and a comparator. The first photodiode receives an optical signal generated by a light emitting element and converts the optical signal into a first electrical signal. The first inverting amplifier is provided with a first feedback resistor and a first operating amplifier connected in parallel with each other. The input end is connected to a cathode of the first photodiode. A first signal which is obtained by inverting the first electrical signal is output from the output end. A second inverting amplifier is provided with a second feedback resistor and a second operating amplifier connected in parallel with each other. The input end of the second inverting amplifier is connected to a cathode of a second photodiode. The second inverting amplifier outputs a second signal from the output end. A comparator receives the first and second signals and outputs a comparison amplified signal. The product of the first junction capacity of the first photodiode and a first feedback resistor and the product of the second junction capacity of the second photodiode and a second feedback resistor are set to be the same value. The second junction capacity is set to be smaller than the first junction capacity.