To provide a bearing device which can ensure the sealing performance by using floating seal to eliminate the need of adding lubricant over a long term and a construction machine comprising the bearing device. The bearing device comprises a shaft. The bearing device comprises a boss portion having a bearing rotatably holding the shaft. The bearing device comprises a cylindrical collar mounted on an end part side of the shaft rather than the boss portion. The bearing device comprises a floating seal for sealing lubricant sandwiched between the boss portion and collar. The bearing device comprises a pin being inserted into the insertion holes provided in the shaft and collar and integrally fixing the shaft and collar at a position where a predetermined axial load is applied to the floating seal between the collar and boss portion. The bearing device comprises a bracket having an opening for mounting the collar.