Résumé : Diffractive electroproduction of ρ and φ mesons is measured at HERA with the H1 detector in the elastic and proton dissociative channels. The data correspond to an integrated luminosity of 51 pb -1. About 10500 ρ and 2000 φ events are analysed in the kinematic range of squared photon virtuality 2.5 ≤Q 2 ≤60 GeV 2, photon-proton centre of mass energy 35 ≤W ≤180 GeV and squared four-momentum transfer to the proton