Chair backrest folding locking mechanism and folding chair

A chair backrest folding locking mechanism, comprising:

• a fixing bracket (1);
• wherein the fixing bracket (1) defines a locking hole (11) disposed transversely;
• a chair backrest (2);
• wherein two sides of a lower end of the chair backrest (2) are hinged on the fixing bracket (1);
• a transverse locking member (3), disposed on the chair backrest (2);
• wherein an outer end of the transverse locking member (3) extends laterally from the lower end of the chair backrest (2), and the transverse locking member (3) is configured to telescopically move relative to the chair backrest (2) in a transverse direction;
• a driving member (4), configured to drive the outer end of the transverse locking member (3) to extend into the locking hole (11);
• a front side resisting part (12), disposed on the fixing bracket (1);
• wherein the front side resisting part (12) is disposed below the chair backrest (2) and located at a side of the chair backrest (2) proximate to a back of a human body;
• and
• a rear side resisting part (21), disposed on the lower end of the chair backrest (2);
• when the chair backrest (2) is in a vertical state, the front side resisting part (12) disposed on the fixing bracket (1) and the rear side resisting part (21) disposed on the chair backrest (2) being arranged in a front and back manner, and a front side of the rear side resisting part (21) being abutted against a rear side of the front side resisting part (12);
• and
• when the transverse locking member (3) is separated from the locking hole (11), the chair backrest (2) being configured to rotate with an angle less than 360° relative to the fixing bracket (1) under an external force.