An infant stroller apparatus includes a leg segment and a handle segment, a joint structure including a first and a second coupling hub that are respectively affixed with the leg segment and the handle segment and are pivotally connected with each other, a mount portion connected with the joint structure, a latch assembly having an actuation surface and arranged in the two coupling hubs, and a detachable seat having a connector and a release actuator arranged adjacent to each other. The latch assembly is movable between a first and a second position for respectively locking and unlocking the leg segment and the handle segment. The release actuator can push against the actuation surface for driving an unlocking displacement of the latch assembly when the seat is installed on the mount portion.