Ten days after the surrender of Japan, after finishing preparations for the final dissolution of the Imperial Japanese Army as dictated by the victorious Allied Powers, Sugiyama committed suicide by shooting himself four times in the chest with his revolver while seated at his desk in his office.
Sepuluh hari setelah Jepang menyerah, setelah ia menyelesaikan persiapan untuk pembubaran Tentara Kekaisaran Jepang karena kemenangan Sekutu, ia bunuh diri dengan menembak dirinya sendiri empat kali di dada dengan pistol sambil duduk di meja kantornya.