Let $M$ be a Riemannian manifold and $TM$ its tangent bundle
with $(1)$ horizontal lift connection, $(2)$ complete lift 
connection, $(3)$ diagonal lift connection or
$(4)$ lift connection {\rm II}$+${\rm III}.
We determine the infinitesimal projective transformations 
on $TM$. Furthermore, if $M$ is complete and $TM$ admits 
a non-affine infinitesimal projective transformation, then 
$M$ and $TM$ are locally flat.