The theory of group thinking is an occurrence where by a group comes to a unanimous decision about a possible action despite the existence of fact that points to another correct course of action. It is the mode of thinking that people engage in when they are deeply involved in a cohesive in-group, when the member' striving for unanimity override their motivation to realistically appraise alternative courses of action.According to Janis Groupthink happens when there is a strong, persuasive group leader, a high level of group cohesion and intense pressure from the outside to make a good decision.Janis listed symptoms to show the agreement hat in the group will have a one or two that have more power to make other believe their thought.So,it can lead to wrong decision because people will ignore the suitability.For example,NASA manager Lawrence Mulloy confirmed that ‘‘no one in the meeting questioned the fact that the secondary seal was capable and in position to seal during the early part of the ignition transient”. They will find reason to support their thought.I claim that to avoid the group thinking is better because the groupthink can lead the damage in working.