Collapsible stroller

A collapsible stroller, comprising:

• a frame, including:
• two front leg tubes, each of the front leg tubes having a first end and a second end on which a wheel is rotatably attached;
• and
• two rear leg tubes, each of the rear leg tubes having a first end pivotally coupled to the front leg tube correspondingly at a vicinity of the first end thereof to form a lateral side of the frame respectively and a second end on which a wheel is rotatably attached;
• a seat unit including two seat side-tubes, each of the side-tubes having a first end pivotally coupled to the front leg tube correspondingly and a second end;
• a collapsing operation unit operably coupled to the seconds of the seat side-tubes, the collapsible stroller being characterized in that:
• when the second ends of the seat side-tubes respectively coupled to rear leg tubes on the corresponding sides of the frame, the collapsing operation unit operably locks the seat side-tubes to the rear leg tubes, and when the collapsing operation unit unlocks and disengages the seat side-tubes from the rear leg tubes, the second ends of the seat side-tubes separate with the rear leg tubes and pivot relative to the front leg tubes.