Touching is a medical action wherein a practitioner touches a patient’s body. Touching has positive physical and mental effects, and is an important technique for nursing. This study examines the effect of touching on patient frustration. To induce frustration, we adopted a mouse pointer-moving game and a calculation task: the game required moving a mouse pointer from the start to the goal without touching walls or obstacles. We asked the participants’ acquaintance to gently touch their backs during the intervention trials. For evaluation, we used power spectral density (PSD) and electroencephalogram (EEG) event-related potential (ERP), and participants’ self-evaluation scores. Theta, alpha, and beta band PSDs increased in frustrating tasks compared to the resting state, however, PSD increments of touching intervention tasks were less than that of control tasks. These results confirm that an acquaintance’s touching can reduce frustration in difficult tasks, and concomitantly reduce unpleasant emotions.