The brain mechanisms underlying anxiety/stress and motivation have been investigated extensively. However, they were mainly investigated independently of each other. Even though some studies discussed interactions between these two mechanisms, our understanding of the interaction between anxiety/stress and motivation is still limited. Motivation can be divided into two aspects. One is appetitive motivation to win appetitive outcome, and the other is aversive motivation for avoiding aversive outcome. Accordingly, in current functional MRI study, it was investigated how appetitive/aversive motivational processing would be influenced by anxiety/stress. In the first experiment I investigated interactions between threat and reward processing during anticipation of electric shock and monetary reward. Analysis of skin conductance data during a delay phase revealed competitive interaction between threat and reward processing. Analysis of imaging data during a delay phase also revealed the interaction effect in several regions, including midbrain/ventral tegmental area, caudate, putamen, bed nucleus of the stria terminalis, anterior insula, middle frontal gyrus, and dorsal anterior cingulate cortex. In the second experiment, the interaction between threat and reward/punishment processing was investigated. Analysis of imaging data during a delay phase revealed competitive interaction between threat and reward processing in left caudate. However, responses in the same site did show interaction between threat and punishment processing. Taken together, the findings in two studies suggest competitive processes of threat and reward, and independent processes of threat and punishment.