We present the X-ray Doppler tomography of the Fe Ka (6.4 keV) fluorescence line of the
low-mass X-ray binary 4U 1822-371 using XRISM. Eleven orbits of this short period (5.57
hr) binary were covered, yielding well-exposed spectra for eight orbital phase bins. A
Doppler shift of the line was modulated by the orbital period, motivating us to apply
the Doppler tomography for the first time in the X-rays. The velocity map has a compact
feature at (vx , vy ) = (-548, +115) km s^-1 . This is inconsistent with the origin of
the emission being in a symmetric disc, an extended corona in the vicinity of the
neutron star, or the surface of the companion star. Rather, it suggests that the
emission originates from the accretion stream and disc impact point on the outer rim of
the disc. Remarkably, the Fe Kα velocity map resembles that of the O VI 3811 A (Casares
et al. 2003), indicating that both X-ray and optical lines arise from the same site
irradiated by the central X-ray source. These results provide the first
velocity-resolved X-ray map of the fluorescent line, directly localizing the principal
reflector in an LMXB and establishing X-ray Doppler tomography as a new probe of the
structures of accreting systems.