The decrease of the semiconductor device and battery market prices gives us the opportunity to perform everyday tasks with unmanned aerial vehicles (UAVs). The most popular UAVs are quadcopters. In my thesis I was investigating the attitude control of these devices. I did a research on the existing solutions and I have designed my own control system. I have built the mathematical model of the quadcopter and I have identificated my test system with the Black-box method. Before I have implemented the controller I got familiar with the commonly used control algorithms. Considering the complexity of the implementation and the roubustness of the final system I have chosen a cascade PID structure. The algorithm was implemented on a flight controller board which was designed by me during a previous project work. With regular PID controllers we can only control linear plants so I had to make changes on the traditional structure to be able to control a nonlinear system. The propellers spinning at high speed make the testing of the quadcopter a difficult and dangerous task, so it was necessary to test the controller step by step. I built my testbench and the data acqusion program to make the test process easier and safer. The final product can maintain stable attitude but lacking a position controller it is difficult to take long flights.