A covariant approach to calculate nuclear effects in deep inelastic scattering on deuteron in the Bethe-Salpeter formalism is proposed. It is shown that Compton amplitude on deuteron can be represented in terms of the BS-vertex function and perturbation expansion of the exact two-nucleon Green function with insertion of electromagnetic operator. Convolution and a nonconvolution parts of the Compton amplitude are separated. Deuteron structure function F2^D is obtained in convolution approximation.