A three-dimensional object manufacturing method is provided and includes: a cavity portion material layer forming step of discharging a droplet of a material from a discharging head through an inkjet method to form a cavity portion material layer, which is a material layer configuring a periphery of at least one part of a cavity; a sandwiching member installing step of installing a lid member, which is a member arranged with at least one part sandwiched between a plurality of material layers, on a cavity portion material layer; and a material layer-on-sandwiching member forming step of discharging the droplet of the cavity portion material from the discharging head through the inkjet method on at least one part of the lid member to further form the material layer on the lid member.