An optical sheet is provided which can be easily processed into formed objects, e.g., a lightguide plate having a reduced thickness and increased area, and has a high light transmittance. Also provided are: a process for producing the optical sheet; a formed object obtained by forming a rugged pattern in a surface of the optical sheet; and a process for producing the formed object. The optical sheet is an optical sheet obtained by extruding an aromatic polycarbonate resin composition from an extruder and then cooling the extrudate at a temperature not higher than the glass transition temperature, the resin composition comprising (A) 100 parts by mass of an aromatic polycarbonate having a viscosity-average molecular weight of 22,000 or lower and (B) 0.01-1 part by mass of an antioxidant and not containing a blue dye or pigment. This optical sheet is characterized in that the optical sheet having a thickness of 0.1-1 mm has a total light transmittance of 91% or higher.