A drinking water supply device may comprise a mineral water supply module comprising a mineral cartridge to store condensed minerals, a mineral supply pipe provided with a micro channel to supply minerals to a water supply pipe, a mineral cartridge receiver detachably coupled to the mineral cartridge and connected to the mineral supply pipe, a mineral supply valve to open and close the mineral supply pipe, and a discharge pipe to discharge filtered water or mineral water. A method of cleaning a drinking water supply device may comprise of discharging residual minerals using a mineral drainage unit including a drainage pipe connected to the mineral supply pipe and a drainage valve to open and close the drainage pipe, supplying cleaning water to a channel in which minerals or mineral water flow of the mineral water supply module, and supplying rinsing water to the channel.