  The edge-on galaxy NGC 4565 has been observed in the 12CO(J=1-0)-line
emission using the Nobeyama 45-m telescope with an angular resolution of 15".
We obtained a scan along the major axis for +/-5' (+/- 15 kpc) about the
galactic center, and some scans perpendicular to the galactic plane. The radial
density distribution shows a dense molecular gas ring of 5 kpc radius, which is
associated with an HI ring. The molecular disk comprises two components: an
unresolved thin and dense disk, and a thick disk (or a halo) extending to a
height greater than 1.4 kpc. The position-velocity diagram shows that the
general rotation of the entire galaxy is circular with a flat rotation curve.
However, the radial distribution of molecular gas is asymmetric with respect to
the galaxy center in the sense that the molecular gas is much richer in the NW
side. We derived a radial variation of \htwo-to-(HI+ \htwo) density ratio, and
found that int erstellar gas in the central 4 kpc region is almost entirely H2,
while HI is dominant beyond 10 kpc. A similar HI-vs-\htwo\ behavior was found
in the edge-on galaxy NGC 891.
