Abstract: A push-the-bit rotary guiding device includes a mandrel having a central passage; a sleeve which is rotatably sleeved outside the mandrel; a plurality of swing ribs which are circumferentially arranged in an outer wall of the sleeve with an interval; an actuation mechanism, for controlling each swing rib to swing respectively; a plurality of detectors, which are circumferentially arranged in the outer wall of the sleeve with an interval, for detecting a distance to a well wall in real-time; and a controller, for determining whether the actuation mechanism is required to actuate the swing ribs to swing according to the detected distance. An application method of the push-the-bit rotary guiding device is provided. According to the push-the-bit rotary guiding device, through a real-time detection of the detectors, a well section having an expanded or reduced diameter is detected in time and guiding of the rotary guiding device herein is avoided.