A ${eta}-1$,3-1,4-glucanase from the fungus Laetiporus sulphureus var. miniatus was purified as a single 26 kDa band by ammonium sulfate precipitation, HiTrap Q HP, and UNO Q ion-exchange chromatography, with a specific activity of 29 U/mg. The molecular mass of the native enzyme was 52 kDa as a dimer by gel filtration. ${eta}-1$,3-1,4-Glucanase showed optimum activity at pH 4.0 and $75^{circ}C$. The half-lives of the enzyme at $70^{circ}C$ and $75^{circ}C$ were 152 h and 22 h, respectively. The enzyme showed the highest activity for barley ${eta}$-glucan as ${eta}-1$,3-1,4-glucan among the tested polysaccharides and p-nitrophenyl-${eta}$-D-glycosides with a $K_m$, of 0.67 mg/ml, a $k_{cat}$ of 13.5 $S^{-1}$ and a $k_{cat}/K_m$ of 20 mg/ml/s.