  The recent measurement on the muon anomalous magnetic moment $a_\mu$ shows a
$2.6\sigma$ deviation from the standard model value. We show that it puts an
interesting bound on the mass of the second generation leptoquarks. To account
for the data the leptoquark must have both the left- and right-handed couplings
to the muon. Assuming that the couplings have electromagnetic strength, the
mass is restricted in the range $0.7 {\rm TeV} < M_{\rm LQ} < 2.2$ TeV at 95%
C.L. We also discuss constraints coming from other low energy and high energy
experiments. If the first-second-generation universality is assumed,
constraints come from the atomic parity violation and charged-current
universality. We show that coexistence with other leptoquarks can satisfy these
additional constraints and at the same time do not affect the $a_\mu$.
