Device holder and device holding system

A device holding system comprising a portable electronic device provided with a display at a front surface thereof and a device holder for holding that portable electronic device, wherein

• the device holder comprises a main body for holding the portable electronic device in a state with the portable electronic device placed with one side surface downward and a swivel block attached to that main body to be able to swivel,
• the main body is provided with a main body connector which is connected to a device connector provided at the side surface of the portable electronic device when the portable electronic device is held at that main body,
• the swivel block is provided at one side surface thereof with an external connector for video output for outputting video data based on data input through the main body connector to an external video display device and is able to swivel between a first swivel position where the side surface, with which the external connector for video output is provided, faces a first side surface side of the portable electronic device held at the main body and a second swivel position where the side surface, with which the external connector for video output is provided, faces a second side surface side at an opposite side to the first side surface of the portable electronic device held at the main body.