A bicycle hydraulic device is basically provided with a base member, a first plug and a second plug. The base member has a hydraulic fluid passageway, a first opening communicating with the hydraulic fluid passageway and a second opening communicating with the hydraulic fluid passageway. The first plug is disposed in the first opening, and having a receiving hole. The second plug is disposed in the second opening. The second plug has a protrusion extending into the receiving hole of the first plug to couple the first and second plugs to the base member.