  The string axion may provide the most attractive solution to the strong CP
problem in QCD. However, the axion energy density easily exceeds the dark
matter density in the present universe due to a large decay constant around
$10^{16}$ GeV, unless the initial value of the axion field is fine-tuned. We
show that this problem is alleviated if and only if the SUSY particle mass
scale is 10-100 TeV, since the decay of the saxion can produce a large enough
amount of entropy after the QCD phase transition, not disturbing the BBN
prediction. The saxion decay also produces a large number of the lightest SUSY
particles (LSPs). As a consequence, R-parity needs to be violated to avoid the
overproduction of the LSPs. The saxion field can be stabilized with relatively
simple Kahler potentials, not inducing a too large axion dark radiation.
Despite the large entropy production, the observed baryon number is explained
by the Affleck-Dine mechanism. Furthermore, the constraint from isocurvature
perturbations is relaxed, and the Hubble constant during inflation can be as
large as several $\times$ $10^{10}$ GeV.
