A bischloroformate composition is represented by a formula (1) below, contains a plurality of Ar components, and has an average number of monomer units (m1), which is calculated by an expression (Numerical Expression 1) below, ranging from 1.0 to 1.99. The plurality of Ar components are each independently Ar1 or Ar2. The plurality of Ar components include at least one Ar1 and at least one Ar2. Ar1 is a group represented by a formula (2) below. Ar2 is a group represented by a formula (3) below. A molar composition ratio represented by Ar1/(Ar1+Ar2) ranges from 45 mol % to 99 mol %. average number of monomer units (m1)=1+(Mav−M1)/M2 (Numerical Expression 1)