1. A liquid ejection head for ejecting a liquid, comprising:a flow passage member, which is composed of a first resin and which is provided with a flow passage configured to come into contact with the liquid;
a liquid supply member bonded to the flow passage member; and
a plurality of resin-coated members having a core-sheath structure composed of a filler constituting an inner core and a second resin constituting an outer core,
wherein the flow passage member comprises the plurality of the resin-coated members.