PRIME B350-PLUS | マザーボード | ASUS 日本 https://www.asus.com/jp/Motherboards/PRIME-B350-PLUS/specifications/
The M.2 Socket shares bandwidth with the SATA6G_5/6 ports, therefore the SATA6G_5/6 ports cannot be used when a SATA/PCIE mode M.2 device is installed.