Wireless power transfer (WPT) is useful for Internet of Things (IoT) in a building. We simulated the electromagnetic-wave propagations from the first floor to the second floor via a building well in a buildings. This simulation result derives the receivable power of IoT devices on the second floor. We also investigated the electric power distribution depending on the position of a transmitting antenna. As a result, we revealed the limitation of transmitting-antenna positions for work IoT devices on the second floor.