The axion has been postulated to solve the strong-CP problem in quantum chromodynamics. The strong-CP problem is manifested by the null observation of the neutron’s electric dipole moment. The Peccei-Quinn U(1) symmetry breaking mechanism was suggested as a solution to the problem. The mechanism leaves a pseudo-Goldstone boson field, interpreted as the axion. Although the original Peccei-Quinn axion model has been ruled out, “invisible” axion model allows a broad range of axion masses and axion-matter couplings. It is widely accepted that the invisible axion is truly the elegant solution to the Strong-CP problem. Moreover, the non-thermal axion production mechanism in the early Universe suggests the axion as a cold dark matter candidate. Especially a light axion is an ideal dark matter candidate which would have been produced during the Big Bang. I will discuss the axion search projects with examples drawn from experiments that I was involved in.