In the Latin Rite, the ordinary minister of Confirmation is the bishop. Although the bishop may for grave reasons concede to priests the faculty of administering Confirmation, it is appropriate from the very meaning of the sacrament that he should confer it himself, mindful that the celebration of Confirmation has been temporally separated from Baptism for this reason. Bishops are the successors of the apostles. They have received the fullness of the sacrament of Holy Orders. The administration of this sacrament by them demonstrates clearly that its effect is to unite those who receive it more closely to the Church, to her apostolic origins, and to her mission of bearing witness to Christ.
Source: Catechism of the Catholic Church (Vatican.va)