This question is the key question of the play. Antigone most obviously has Sophocles' sympathy, yet she is as headstrong, prideful, unwilling to compromise as her uncle. The play is skillfully balanced. We see Creon's need to establish order, to maintain his authority, to punish those that would bring violence to the city-state. But we also see Antigone's fierce loyalty to her family, her gods, her own integrity. The chorus warns each of them about their unwillingness to bend.
At the heart of the play is a question of priorities and the consequences when priorities clash. Neither character is evil. Neither is clearly wrong or clearly right. Neither will listen to the other. Each is certain of his/her rightness. Either course seems to exclude the other--or does it? Is Ismene's willingness to let things be a suitable course of action? Is Haemon's reasoned approach better? Perhaps what should be done could be better answered by looking more closely at the minor characters and at the chorus.
It sure seems to me he does take a side. How Sophocles chooses to characterize each of the principle players tells me he sides with Antigone.
Ismene is weak and submissive, accepting what is without question or action.
Antigone is strong and passionate about doing what's right, whatever the cost.
Haemon is an obedient son; however, once he recognizes his father's unwillingness to bend in the least for those who matter most to him or to see reason, he sides with Antigone.
Creon is arrogant and prideful--unwilling to bend even for his neice/future daughter-in-law and his nephew. Ego and being right matter more to him than anything else.
In the end, all three suffer for their actions; clearly, though, the root of all these tragedies is Creon's pride. His law (state law) is unjust in that he decrees it out of pride and personal revenge. That tells me Antigone is on the side of righteousness, according to Sophocles, because she chooses moral law over an unjust state law. He clearly outlines the consequence of such disobedience, but he is most sympathetic, I think, to Antgone's cause.