  This paper reports an experimental demonstration of moir\'e metalens which
shows wide focal length tunability from negative to positive by mutual angle
rotation at the wavelength of 900 nm. The moir\'e metalens was developed using
high index contrast transmitarray meta-atoms made of amorphous silicon
octagonal pillars, which is designed to have polarization insensitivity and
full 2$\pi$ phase coverage. The fabricated moir\'e metalens showed focal length
tunability at the ranges between $\pm$1.73 -- $\pm$5 mm, which corresponds to
the optical power ranges between $\pm$578 -- $\pm$200 m$^{-1}$ at the mutual
rotation between $\pm$90 degrees.
