Nowadays, the world is experiencing an increasing boom in applications of artificial intelligence, especially deep learning. This is more and more used in many areas such as industry, medicine and security systems, etc. This article deals with object detection from Unmanned Aerial Vehicle (UAV) perspective. The whole system uses one camera, which is suitably positioned on the UAV to capture the scene. Image processing and subsequent object detection using the YOLOv4 model are performed on the Jetson Nano device. The device itself is relatively powerful, but to save the computing power of the device, the YOLOv4 neural network model was modified. The YOLOv4 model was trained on our own dataset. This training set was created specifically for UAV applications. The result of this work is a learned YOLOv4 neural network model designed for UAVs with regard to the used training set. The modified network model is also able to run in real-time and save computing power for possibly other UAV operations. All materials, dataset and scripts used in this work, are available at https://github.com/KicoSVK/object-detection-in-uav-using-yolov4.