Roberto Soldado's second-minute strike had given the hosts an early lead but they were never in control and were pegged back before half-time as Alberto de la Bella fired in an equaliser minutes after Jonas had seen a straight red card for lashing out at David Zurutuza.
Sociedad took control in the second period as further goals from Mikel Gonzalez, Diego Ifran, Imanol Agirretxe and Carlos Vela rendered Soldado's second of the evening meaningless.
A first home defeat of the season for Valencia sees them slip to 12th, but they had got off to the perfect start as a fantastic crossfield pass from Fernando Gago found Juan Bernat on the left and his low driven cross was slotted home at the near post by Soldado.
Sociedad thereafter and would have gone in at half-time comfortably ahead had it not been for the heroics of Diego Alves.
The Brazilian was first called into action on 14 minutes when Vela released Antoine Griezmann but Alves got just enough on the Frenchman's shot to turn it onto the post.
Alves then denied Vela from a narrow angle before producing two world-class saves to turn an Ifran effort behind when he was one-on-one and then getting an outstretched hand to turn Xabi Prieto's looping header over.
Valencia's task was made even tougher five minutes before half-time when Jonas was shown a straight red card for elbowing Zurutuza and Sociedad took advantage three minutes later when Zurutuza found De la Bella and he left Alves helpless with a lovely finish into the far corner.
The visitors continued to make their man advantage count after the break and looked to have killed the game off when Gonzalez headed in at the far post from Prieto's flick-on and Ifran finished off a fine counter-attack by sliding in after rounding Alves.
Valencia did offer some resistance when another fine finish from Soldado after Sofiane Feghouli's cross reduced the arrears.
Any hopes of a comeback were quashed eight minutes from time when Agirretxe showed good awareness to latch onto Chori Castro's deflected knockdown to round Alves and make it 4-2.
And the Basques sealed their second consecutive away win when Vela was brought down by Feghouli in stoppage time and picked himself up to roll home his sixth goal of the season from the penalty spot.