Characteristics of the post-ionization using femto-second laser (fs laser) combined with the secondary ion mass spectrometer were investigated. For many metals, ionization saturations were confirmed for the laser power density of >2 x 10(13) W/cm(2). The characteristic curve of ionization of Ag against the laser power density suggests the occurrence of ionization through the multi-photon resonance excitation. Sensitivity increase after employing the fs laser post-ionization was manifested and a sputtered Cu signal from a minute circular area with a diameter of about 200 nm could be detected clearly. (C) 2008 Elsevier B. V. All rights reserved.