The leaders were in uninspired form against the Basque side who can count themselves unlucky not to have claimed their first win in six outings in a game they dominated from start to finish.
Sociedad, who ran Real so close for the title last season but have struggled so far this term, had two goals disallowed in the first half and enjoyed a host of scoring opportunities in the second, but were unable to clinch the win they deserved.
The result leaves Valencia a point clear of Real Madrid, but the champions can regain top spot if they beat city rivals Atletico in Wednesday's Madrid derby.
Third-placed Deportivo Coruna, who are a further point behind Real, could also overhaul Valencia if they win their match away to Valladolid.
Sociedad started positively and looked to have taken an early lead when Valery Karpin poked the ball in on three minutes, but the Russian's goal was ruled out for a non-existent offside.
The home side had the ball in the net once more on 32 minutes when Darko Kovacevic turned his defender and cracked in from the edge of the box but again the goal was disallowed, this time for a foul by the powerfully built striker.
Valencia, who had hardly threatened in the first half, looked more lively at the start of the second and finally produced a shot on target when midfielder Carlos Marchena unleashed a powerful drive from the edge of the area, only to be denied by a fine one-handed save from Sander Westerveld.
But it was Sociedad who continued to show more ambition and they were desperately unlucky not to score midway through the half when substitute Nihat Kahveci slammed a powerful drive against the bar and Igor Gabilondo had successive goal-bound shots cleared off the line.
Valencia could have stolen victory, though, when Francisco Rufete raced free 17 minutes from time, but the midfielder sliced his shot wide of the post after he had done all the hard work and rounded keeper Westerveld.
The result leaves Sociedad just three points clear of the relegation zone, with all their immediate rivals yet to play.
