A bicycle hydraulic device comprises a base member and a cover member. The base member is configured to be mounted to a bicycle body. The base member comprises a hydraulic bore and an insertion portion. The hydraulic bore has a first end and a second end. The first end defines a first opening. The insertion portion is provided between the first end and the second end. The insertion portion includes an insertion opening different from the first opening. The cover member is provided at the insertion portion via the insertion opening to cover the hydraulic bore.