Recently, double-well optical lattices have been created to trap bosonic atoms by an experimental group at NIST. In this talk, I will discuss the superfluid-to-Mott insulator transition of bosons in double-well optical lattices. The zero-temperature phase diagrams of the two-leg Bose-Hubbard model are calculated by means of the time-evolving block decimation algorithm [G. Vidal, Phys. Rev. Lett. 98, 070201 (2007)].