James Holmes, 24, sat in court in a red jail suit with dyed orange hair, and appeared sleepy during the proceedings.
Nine of 58 people wounded by the gunman remain in critical condition.
On Sunday, President Barack Obama met survivors and families of the dead as hundreds of people took part in a service of remembrance.
Mr Holmes is to be held without bail at a jail in Centennial, Colorado, the judge said.
Mr Holmes is accused of throwing two canisters of gas into a busy midnight screening of The Dark Knight Rises before firing at random at the crowd. Witnesses say he was wearing full body armour during the attack.