  High-mass star formation is an important step which controls galactic
evolution. GM 24 is a heavily obscured star cluster including a single O9 star
with more than $\sim$100 lower mass stars within a 0.3 pc radius toward
$(l,b)\sim$ (350.$^{\circ}$5, 0.$^{\circ}$96), close to the Galactic
min-starburst NGC 6334. We found two velocity components associated with the
cluster by new observations of $^{12}$CO $J=$ 2-1 emission, whereas the cloud
was previously considered to be single. We found the distribution of the two
components of $5$ km s$^{-1}$ separation shows complementary distribution which
fits well with each other, if a relative displacement of 3 pc is applied along
the Galactic plane. A position-velocity diagram of the GM 24 cloud is explained
by a model based on the numerical simulations of two colliding clouds, where an
intermediate velocity component created by collision is taken into account. We
estimate the collision time scale to be $\sim$Myr in projection of a relative
motion titled to the line of sight by 45 degrees. The results lend further
support for cloud-cloud collision as a major mechanism of high-mass star
formation in the Carina-Sagittarius Arm.
