Rotary damper and production method therefor

A method of manufacturing a rotary damper comprising a cylinder having a partition wall;

• a rotor having a shaft portion opposing the partition wall;
• a first recess formed on a distal end surface of the partition wall;
• an elastic body installed in the first recess and closely contacting the shaft portion to seal a gap between the partition wall and the shaft portion;
• and a second recess formed in a part of an outer peripheral surface of the shaft portion not opposing the distal end surface of the partition wall during operation, the method comprising the steps of:
• forming a space consisting of a combination of the first recess and the second recess by facing an opening of the second recess to an opening of the first recess, and
• inserting the elastic body into the space without compression.