Damping force generating mechanism and pressure shock absorber

A damping force generating mechanism comprising:

• a valve that is configured to control a flow of a liquid in a flow passage through which the liquid flows;
• a flow passage formation part including
• a first seat part that is provided radially outward of a flow passage port of the flow passage, protrudes from the flow passage port and contacts the valve,
• a second seat part that is provided radially outward of the first seat part, protrudes from the flow passage port and contacts the valve, and
• a circulation part having an orifice that allows the liquid to flow from the flow passage port toward the second seat part in a state in which the valve is in contact with the first seat part;
• and
• a back pressure chamber formation part that forms a back pressure chamber for applying a back pressure to the valve, wherein
• the back pressure chamber formation part includes a contact part that annularly contacts with the valve radially inward of a position of the second seat part to form a range in which the back pressure is applied to the valve and another range in which the back pressure is not applied to the valve.