To provide a resin composition having a low coefficient of linear expansion, high transparency, a low coefficient of hygroscopic expansion, heat resistance, and high strength/high elasticity.

An organized fiber contains a microcellulose fiber having a diameter of 4-1,000 nm and an organic cationic compound. The resin composition further contains a hydrophobic resin in addition thereto. In the resin composition, the microcellulose fiber is preferably a fiber obtained by carrying out fining with a chemical treatment and/or a mechanical treatment, and a part of hydroxyl groups of the cellulose fiber are oxidized into aldehyde groups or/and carboxy groups. The organic cationic compound is more preferably a nitrogen-containing compound or a phosphorus-containing compound.