A substrate storage container comprising: a container casing having an aperture through which a plurality of substrates are placed in or taken out; a cover adapted to fit into said aperture of said container casing; a sealing gasket capable of elastic deformation provided between said container casing and said cover; and a retainer, mounted on said cover, capable of retaining the periphery of each of the substrates; said retainer having: a supporting body mounted on the inside face of said cover, wherein the supporting body comprises a pair of first bars positioned on left and right sides with a separation therebetween; a plurality of elastic pieces provided in elastically deformable fashion on said supporting body and extending in the left and right transverse direction between the first pair of bars and arranged in the vertical direction with prescribed separation; a slit formed at the sides of the plurality of elastic pieces; and a block provided on each of said elastic pieces, said block retaining the periphery of one of said substrates; characterized in that: the plurality of elastic pieces extend in the left and right transverse direction so as to deformably span the space between the first pair of bars; and 10.8 × w < y < 34.3 × w when a substrate retaining force of each of said elastic pieces is y [unit: N] and a weight per said substrate is w [unit: kg]. a container casing having an aperture through which a plurality of substrates are placed in or taken out; a cover adapted to fit into said aperture of said container casing; a sealing gasket capable of elastic deformation provided between said container casing and said cover; and a retainer, mounted on said cover, capable of retaining the periphery of each of the substrates; said retainer having: a supporting body mounted on the inside face of said cover, wherein the supporting body comprises a pair of first bars positioned on left and right sides with a separation therebetween; a plurality of elastic pieces provided in elastically deformable fashion on said supporting body and extending in the left and right transverse direction between the first pair of bars and arranged in the vertical direction with prescribed separation; a slit formed at the sides of the plurality of elastic pieces; and a block provided on each of said elastic pieces, said block retaining the periphery of one of said substrates; characterized in that: the plurality of elastic pieces extend in the left and right transverse direction so as to deformably span the space between the first pair of bars; and 10.8 × w < y < 34.3 × w a supporting body mounted on the inside face of said cover, wherein the supporting body comprises a pair of first bars positioned on left and right sides with a separation therebetween; a plurality of elastic pieces provided in elastically deformable fashion on said supporting body and extending in the left and right transverse direction between the first pair of bars and arranged in the vertical direction with prescribed separation; a slit formed at the sides of the plurality of elastic pieces; and a block provided on each of said elastic pieces, said block retaining the periphery of one of said substrates; characterized in that: the plurality of elastic pieces extend in the left and right transverse direction so as to deformably span the space between the first pair of bars; and 10.8 × w < y < 34.3 × w when a substrate retaining force of each of said elastic pieces is y [unit: N] and a weight per said substrate is w [unit: kg].