It is crucial for animals to select an appropriate behavior in a conflict situation where they are simultaneously faced with positive and negative motivations. But the neural mechanism underlying behavioral selection in a conflict situation is unclear. We set up a behavioral paradigm in which mice needed to explore an experimental context where they might receive electric shocks in order to obtain sucrose. Previously, we reported that neuronal pathway from the anterior cingulate cortex (ACC) to the periaqueductal gray (PAG) was activated when mice were seeking sucrose in a conflict situation. In this study, we tested causal relationships between the ACC-PAG activity and reward-seeking behaviors. Optogenetic activation or inhibition of the ACC-PAG pathway shortened or prolonged the latency to obtain sucrose, respectively. In order to examine the possibility that the manipulation of the ACC-PAG pathway may change appetite of animals, we allowed mice to freely access to sucrose solution in an open field and measured the time to consume sucrose solution. Neither optogenetic activation nor inhibition of the ACC-PAG pathway changed the time to consume sucrose solution. These results suggest that activation of the ACC-PAG pathway promotes reward-seeking behaviors in a conflict context without changing appetite.