  The ubiquitousness of solar inter-network horizontal magnetic field has been
revealed by the space-borne observations with high spatial resolution and
polarization sensitivity. However, no consensus has been achieved on the origin
of the horizontal field among solar physicists. For a better understanding, in
this study we analyze the cyclic variation of inter-network horizontal field by
using the spectro-polarimeter observations provided by Solar Optical Telescope
on board Hinode, covering the interval from 2008 April to 2015 February. The
method of wavelength integration is adopted to achieve a high signal-to-noise
ratio. It is found that from 2008 to 2015 the inter-network horizontal field
does not vary when solar activity increases, and the average flux density of
inter-network horizontal field is 87$\pm$1 G, In addition, the imbalance
between horizontal and vertical field also keeps invariant within the scope of
deviation, i.e., 8.7$\pm$0.5, from the solar minimum to maximum of solar cycle
24. This result confirms that the inter-network horizontal field is independent
of sunspot cycle. The revelation favors the idea that a local dynamo is
creating and maintaining the solar inter-network horizontal field.
