A duct opening portion structure includes an air intake duct; a filter that is disposed in an opening portion at an air introduction side of the air intake duct; and a bezel that is disposed in the opening portion at the air introduction side of the air intake duct, the bezel being configured to support the filter. The bezel is attached to a vehicle body-side member, and the bezel includes a rib including a support portion configured to support the filter. The filter is attached to the support portion. The rib is provided with an extension portion having a length that allows the extension portion to be directly or indirectly pressed against a seal member provided at an edge of the opening portion in a state where the bezel is attached to the vehicle body-side member.