The optical absorption spectrum of a vanadium tetramer ion, V-4(+), was Obtained by measuring a photodissociation efficiency of an ion complex, V-4(+) Ar, as a function of the photon energy of the laser pulse used for the photodissociation. The optical absorption spectrum thus obtained was simulated by a density functional calculation to search for the most probable geometric structure which reproduces the measured spectrum. The analysis showed that V-4(+) is most likely to have a ＇＇distorted＇＇ tetrahedral structure with C-2 upsilon symmetry. The ground electronic state of V-4(+) was found to be a low spin state, (2)A(1). The relatively broad spectral profile is explained in terms of the distortion related to a low-energy vibration. Geometry optimization;of the Amsterdam density functional (ADF) calculation also predicts C-2 upsilon Symmetry for the structure of V-4(+).