Proton and neutron electromagnetic form factor and charge radius in lattice QCD

We report our recent study of nucleon electromagnetic form factor and its charge radius in lattice QCD. We compute the form factor using large size of lattice volume, more than 8 fm³, at (almost) physical pion mass which is the first realistic computation by reducing the systematic errors of the finite size correction and chiral extrapolation. We present preliminary results of not only isovector form factor but also isoscalar one, and discuss a comparison with experimental result.