A bubble generating device is disclosed which includes: a bubble generator including a tubular body, a liquid introduction port, a gas introduction port, and a discharge port; and a gas supply unit including a gas supply port, a pressurized gas being supplied to the bubble generator through the gas supply port, wherein the flow passage of the bubble generator extends substantially along a same axis, a plurality of reduced diameter portions each having an inner diameter reduced are provided along a direction along which the liquid flows, and gas-liquid mixing portions are provided downstream of the respective reduced diameter portions in a contiguous manner, each of the gas-liquid mixing portions having an inner diameter larger than a minimum inner diameter of each of the plurality of reduced diameter portions, and the gas introduction port of the bubble generator is formed of a plurality of through holes.