To provide an IC package substrate holding body that is used for holding IC package substrates on washing the IC package substrates and is capable of effectively preventing the IC package substrates from popping out from fixed positions during the process of washing even though a tray is deformed by warp or the like.

An IC package substrate holding body is composed of a tray 20 that is equipped with partition parts 22 each formed approximately in a latticelike shape for arranging each of IC package substrates at respective positions, indented parts 23 each formed at four sides of the partition part 22 respectively corresponding to four sides of the IC package substrate, and tray-side openings 24 each formed at a position whereon the IC package substrate is mounted and a synthetic resin lid for covering the upside of the IC package substrates mounted on the tray 20 and preventing the IC package substrates from popping out during the process of washing. The lid is equipped with protuberances 25 each projecting from the upside to the downside to intrude into the indented part 23 and lid-side openings each formed at a position whereto the IC package substrate faces.