This study was carried out to investigate the effect of bonding temperature and holding time on microstructure and mechanical properties in brazing joints of Ni-base superalloy using MBF-30 (Ni-4.5Si-3.2B [wt.%]). The heating rate was $20^{circ}C$/min to the bonding temperatures $1050^{circ}C$, $1070^{circ}C$, $1090^{circ}C$ under high vacuum condition. The holding times were 100s, 400s, 900s and 1600s. $Ni_3B$ phases and proeutectic Ni were observed in the interlayer of Ni-201. Then, Ni3B and Ni3Si were found in the middle region of brazing joint. Cr-boride phase appeared in the interlayer of Inconel-625. Tensile strength and elongation were decreased at $1050^{circ}C$-1600s, $1070^{circ}C$-900s and $1090^{circ}C$-400s. After observation the fracture specimens, There was Ni3B which is very brittle phase in the grain boundary of Ni201.