De la Bella netted in the 69th minute as the hosts extended their unbeaten record to eight matches in all competitions, while Sevilla have now collected just one point from their last five league matches.
The visitors did get back on level terms as Gary Medel cancelled out Carlos Vela's early strike, but De la Bella ensured they went home empty-handed and their misery was further compounded when Andujar Coke picked up two yellow cards in the space of four second-half minutes.
The result moved Sociedad up to seventh although it was a welcome triumph for Philippe Montanier's men, who had won just two of their last seven before tonight.
They started to take charge in the early stages with Xabi Prieto firing wide while Diego Ifran was just beaten to Antoine Griezmann's cross by Coke.
And the hosts were rewarded for their early endeavour in the 18th minute when Vela gave them the lead when he fizzed a low strike past Sevilla goalkeeper Diego Lopez after collecting the ball from Griezmann.
The goal seemed to suck the confidence out of Sevilla, who nearly fell two behind after the interval when Prieto somehow fired over from Griezmann's cross.
That seemed to act as a wake-up call to Los Rojiblancos and they levelled in the 49th minute, with Medel expertly curling past Sociedad shot-stopper Claudio Bravo from the edge of the area.
Jose Antonio Reyes went close for the visitors with a fine strike but this time, Bravo was able to tip away.
It proved a vital save as Carlos Martinez burst up the other end and his right-wing cross was converted at the back post by fellow full-back De la Bella.
Things were about to get worse for Sevilla as Coke was dismissed for a second bookable offence in the 74th minute for a foul on Vela - having just been cautioned for a cynical challenge on De la Bella.
It was an unnecessary foul and one that looked to have cost Sevilla although Bravo did have to tip Alvaro Negredo's close-range header round the post in the closing stages as Sociedad held on for all three points.