A buckle in a seatbelt apparatus comprising: a buckle stay that has a fixation portion (15, 22) provided at a base end of the buckle stay and fixed to a vehicle body, and a coupling plate portion provided at a leading end of the buckle stay and having a through-hole (13, 23); a buckle base having a bottom plate portion and a pair of side plate portions standing up from opposite side edges of the bottom plate portion, the buckle base also having a through-hole (13, 23) formed at one end of the bottom plate portion in a length direction of the bottom plate portion; a support shaft inserted through the through-holes (13, 23) in the coupling plate portion of the buckle stay and at the one end of the bottom plate portion, the support shaft being loosely inserted through the through-hole (13, 23) in the coupling plate portion, to allow the buckle base to be coupled to the buckle stay so as to be able to tilt, with respect to the buckle stay, through a predetermined angle in a first direction perpendicular to a plate surface of the bottom plate portion and so as to be able to pivot, with respect to the buckle stay, through a predetermined angle in a second direction parallel to the plate surface of the bottom plate portion; and an elastic member that is, when the buckle base tilts in the first direction and pivots in the second direction, pushed by the buckle stay and elastically deformed so as to return the buckle base to an original position, wherein the support shaft has a pair of arm portions provided at an upper portion of the support shaft and extending in a lateral direction, and tip portions of the pair of arm portions are coupled into respective engagement grooves formed in the pair of side plate portions to couple the support shaft directly to the side plate portion of the buckle base, characterized in that the through hole is provided with an inclined portion enabling the buckle stay to be tilted while avoiding interference with the support shaft when the buckle stay is tilted to the buckle base. a buckle stay that has a fixation portion (15, 22) provided at a base end of the buckle stay and fixed to a vehicle body, and a coupling plate portion provided at a leading end of the buckle stay and having a through-hole (13, 23); a buckle base having a bottom plate portion and a pair of side plate portions standing up from opposite side edges of the bottom plate portion, the buckle base also having a through-hole (13, 23) formed at one end of the bottom plate portion in a length direction of the bottom plate portion; a support shaft inserted through the through-holes (13, 23) in the coupling plate portion of the buckle stay and at the one end of the bottom plate portion, the support shaft being loosely inserted through the through-hole (13, 23) in the coupling plate portion, to allow the buckle base to be coupled to the buckle stay so as to be able to tilt, with respect to the buckle stay, through a predetermined angle in a first direction perpendicular to a plate surface of the bottom plate portion and so as to be able to pivot, with respect to the buckle stay, through a predetermined angle in a second direction parallel to the plate surface of the bottom plate portion; and an elastic member that is, when the buckle base tilts in the first direction and pivots in the second direction, pushed by the buckle stay and elastically deformed so as to return the buckle base to an original position, wherein the support shaft has a pair of arm portions provided at an upper portion of the support shaft and extending in a lateral direction, and tip portions of the pair of arm portions are coupled into respective engagement grooves formed in the pair of side plate portions to couple the support shaft directly to the side plate portion of the buckle base, characterized in that the through hole is provided with an inclined portion enabling the buckle stay to be tilted while avoiding interference with the support shaft when the buckle stay is tilted to the buckle base.