We present a structural study of the hot ISM in the Galactic halo along the sight line toward the bright active galactic nucleus Mkn 421 . The O \emissiontype VII and O \emissiontype VIII absorption lines were measured with the Low Energy Transmission Grating Spectrograph aboard Chandra toward Mkn 421 , and the O \emissiontype VII and O \emissiontype VIII emission lines were observed in the adjacent fields of the sight line with the X-ray Imaging Spectrometer aboard Suzaku . We jointly analyzed the absorption and the emission spectra assuming exponential distributions of the gas temperature and density from the Galactic plane , and constrained the temperature and density at the plane to be ( 3.2 ^ { +0.6 } _ { -0.7 } ) \times 10 ^ { 6 } \mathrm { K } and ( 1.2 ^ { +0.5 } _ { -0.4 } ) \times 10 ^ { -3 } \mathrm { cm ^ { -3 } } , with the scale heights of 1.6 ^ { +1.7 } _ { -0.7 } \mathrm { kpc } and > 2.8 \mathrm { kpc } respectively . The results are consistent with those obtained in the LMC X–3 direction and the PKS 2155–304 direction , describing a thick disk-like hot gas with its height of a few kpc from the Galactic plane .