To provide polyester-based binder fiber for Shoji paper that can produce Shoji paper having homogeneous texture and high strength.

The polyester-based binder fiber for Shoji paper has a sheet area shrinkage percent of ≤30 and a fiber length of 3-25mm. The sheet area shrinkage percent is given by the following procedures: a square sheet machine is used to well stir/mix 80wt.% of the polyester binder fiber for Shoji paper and 20wt.% of NBKP in water to disperse the fiber and prepare sheets of a size of about 25cm×25cm with the weight basis of about 50g/m2, then, the sheets are dried at room temperature for more than one day and night, each placed on a perforated Teflon (R) sheet. Then, one of the sheets is heated in a hot-air circulation drier at 120°C and subjected to relaxation shrinkage treatment for 5 minutes and calculate by the formula, {(A0-A1)/A0}x100 (wherein AO is the sheet area before the shrinkage treatment and A1 means the area after the treatment).