This diploma thesis deals with the design of low-power IoT device communicating by using the NB-IoT standard. The theoretical part of the thesis is dedicated to the explanation of the principles and capabilities of communication in IoT networks Sigfox, LoRa and NB-IoT, and also its physical layer, network architecture, techonology principles and frequency bands used. The application part of the thesis is dedicated to design of the NB-IoT device from the system design through the selection of main components to the detailed physical design of the device. Two prototypes of the device with two different radio modules used are fabricated on which is performed measurement of the power profile of the device in various operation modes.