Administrative procedure is a set of legal rules regulating the manner in which a state administration body operates when, by applying substantive legal regulations to a specific social relationship, it decides on the rights, obligations or legal interests of individuals. In administrative proceedings, public law bodies deciding on the rights and obligations of individuals pass administrative acts (decisions). A natural or legal person whose request is the subject of administrative proceedings or who is the subject of administrative proceedings or who is entitled to participate in administrative proceedings for the protection of his rights or interests may appear as a party to administrative proceedings. In addition to natural and legal persons in administrative proceedings, state administration bodies may appear as a party if they may be bearer of rights or obligations decided in administrative proceedings. Parties to administrative proceedings have certain rights, one of which is the right of a party to a judicial remedy. It is a constitutional and legal right of citizens as well as a universal human right because it is recognised in numerous international documents. As a regular and strongest remedy available to citizens in the fight against illegal and irregular legal acts, we know the appeal, which has been elaborated in detail in this paper. The last part of this paper refers to the procedural rule prohibiting reformation in peius. The paper also deals with the case-law relevant to this procedural rule.