The article is devoted not just to historical analysis of the Roman republican structures, but to the revealing of historical backgrounds of the institutes of democracy that we have today. In fact the Romans were the first who established the stable and viable institutes based on democratic principles and able to survive even great civil wars of the late Republic and to transform into effective mechanism of state management during the period of Empire. What was called in the ages of Rome “magistracy” today is called “state machine”. In other words it is the number of public offices responsible for efficient functioning of the country. The Roman Magistrates were elected officials in Ancient Rome. During the period of the Roman Kingdom, the King of Rome was the principal executive magistrate. His power, in practice, was absolute. He was the chief priest, lawgiver, judge, and the sole commander of the army. When the king died, his power reverted to the Roman Senate, which then chose an Interrex to facilitate the election of a new king. During the transition from monarchy to republic, the constitutional balance of power shifted from the executive (the Roman King) to the Roman Senate. When the Roman Republic was founded in 509 BC, the powers that had been held by the king were transferred to the Roman Consuls, of which two were to be elected each year. Magistrates of the republic were elected by the People of Rome, and were each vested with a degree of power, called "major powers" ( maior potestas ). Dictators had more "major powers" than any other magistrate, and after the Dictator was the Censor, and then the Consul, and then the Praetor, and then the Curule Aedile, and then the Quaestor. Any magistrate could obstruct ("veto") an action that was being taken by a magistrate with an equal or lower degree of magisterial powers. By definition, Plebeian Tribunes and Plebeian Aediles were technically not magistrates since they were elected only by the Plebeians, and as such, they were independent of all other magistrates. Looking through the history of Ancient Rome since the period of Monarchy to the period of Empire the authors are going to reveal the main principles of functioning of magistracies as the executive element of the Roman state. Researching the issue the authors used methodology of historical science: the method of analysis, the method of keys and the comparative method of historical research.