We present 7 sequential weekly observations of NGC 5548 conducted in 2007 with the Suzaku X-ray Imaging Spectrometer ( XIS ) in the 0.2-12 keV band and Hard X-ray Detector ( HXD ) in 10-600 keV band .
The iron K \alpha line is well detected in all seven observations and K \beta line is also detected in four observations .
In this paper , we investigate the origin of the Fe K lines using both the width of the line and the reverberation mapping method .

With the co-added XIS and HXD spectra , we identify Fe K \alpha and K \beta line at 6.396 _ { -0.007 } ^ { +0.009 } keV and 7.08 _ { -0.05 } ^ { +0.05 } keV , respectively .
The width of line obtained from the co-added spectra is 38 _ { -18 } ^ { +16 } eV ( \textrm { FWHM } = 4200 _ { -2000 } ^ { +1800 } km/s ) which corresponds to a radius of 20 _ { -10 } ^ { +50 } light days , for the virial production of 1.220 \times 10 ^ { 7 } M _ { \odot } in NCG 5548 .

To quantitatively investigate the origin of the narrow Fe line by the reverberation mapping method , we compare the observed light curves of Fe K \alpha line with the predicted ones , which are obtained by convolving the continuum light curve with the transfer functions in a thin shell and an inclined disk .
The best-fit result is given by the disk case with i = 30 ^ { \circ } which is better than a fit to a constant flux of the Fe K line at the 92.7 % level ( F-test ) .
However , the results with other geometries are also acceptable ( P > 50 % ) .
We find that the emitting radius obtained from the light curve is 25-37 light days , which is consistent with the radius derived from the Fe K line width .
Combining the results of the line width and variation , the most likely site for the origin of the narrow iron lines is 20-40 light days away from the central engine , though other possibilities are not completely ruled out .
This radius is larger than the H \beta emitting parts of the broad line region at 6-10 light days ( obtained by the simultaneous optical observation ) , and smaller than the inner radius of the hot dust in NGC 5548 ( at about 50 light days ) .