Next generation wireless communication technology of Internet of Things (IoT) nowadays is already used in many use cases. In 2016 3GPP) started introducing a new technology called Narrowband Internet of Things (NB-IoT). Targeting to serve the market of IoT devices, NB-IoT is designed to be better in dealing with large number of subscriber equipments or IoT devices in a cell, compared to the existing cellular technologies. The biggest challenge to serve large number of connecting devices in wireless technologies is the random access, which serves as an entrance gate for the devices demanding physical resources for data transmission. This paper presents a simulation result of NB-IoT's random access procedure under massive number of devices in steady-state condition. A backoff mechanism with retry limit is considered with one coverage enhancement level. The result shows that a probability of transmitting packet also has a role in performance, where the higher of probability to generate uplink packet, the higher the lost packet will occur.