Abstract: The present invention provides a bearing device reliable of shielding any material or fluid from moving between a fluid passage within a fluid system housing and an outside of the housing. In the above bearing device, a roller bearing (12) equipped with sealing plates (17) is fitted into a coupling bore (11) in an intake pipe (1) serving as the housing so that the roller bearing (12) can bear a shaft (6) of a butterfly valve disposed in a fluid passage (2) within the intake pipe (1). The outer race (13) and the inner race (14) of the roller bearing (12) are formed with annular grooves (21, 22), respectively, and O-rings (23, 24) are engagingly arranged on the interior of the annular grooves (21, 22), respectively. With the bearing device having this structure, the O-rings (23, 24) can prevent air, etc. from permeating into the intake passage (2) even though clearance (a, b) occurs in the engaged sections due to a dimensional error, difference in thermal expansion, etc.