We present the results of a search for variable stars in a photometric survey of a six square degree region along the Galactic plane at (l=305{deg}, b=-0.8{deg}) and (l=330{deg}, b=-2.5{deg}). This survey was performed in the framework of the EROS II (Experience de Recherche d'Objets Sombres) microlensing program. The variable stars were found among 1913576 stars that were monitored between April and June 1998 in two passbands, with an average of 60 measurements. For the periodicity search, a new method is proposed well suited when the photometric data are unevenly distributed in time, as is our case. 1362 objects whose luminosity varies were selected. Among them we identified 9 Cepheids, 19 RR Lyrae, 34 Miras, 176 eclipsing binaries and 266 Semi-Regular stars. Most of them are newly identified objects. The cross-identification with known catalogues has been performed. Our catalogue and light curves are available from our Web site (http://www.lal.in2p3.fr/recherche/eros/GSA/EROS2-GSA-periodic.html)