Understanding the molecular mechanism of neuronal differentiation is extremely important to overcome the incurable diseases caused by nervous system damage. Neurite outgrowth is essential for neuronal differentiation and regeneration, and cAMP response element-binding protein (CREB) is one of the key transcriptional factors positively regulating this process. Neuronal differentiation stimuli activate mammalian target of rapamycin complex 2 (mTORC2) / Akt signaling to phosphorylate CREB. However, the molecular mechanism that regulates the activity of this signaling remains poorly understood. We found that neuronal differentiation stimuli increased a protein level of protein phosphatase 6 (PP6), a member of type 2A Ser/Thr protein phosphatases in N2a cells and mouse ES cells. The decrease in autophagy activity was suggested to be involved in the stimulation-induced increase in PP6 expression. PP6 knockdown suppressed mTORC2/Akt/CREB signaling and failed neurite outgrowth. SIN1 is a unique component of mTORC2, and dephosphorylation of SIN1 increases the activity of mTORC2 against Akt. We found PP6 knockdown increased SIN1 phosphorylation. These data suggest that PP6 may positively regulate neurite outgrowth by dephosphorylating SIN1 to activate mTORC2/Akt/CREB signaling.