Victivallis vadensis ATCC BAA-548 is a Gram-negative, anaerobic bacterium that was isolated from a human fecal sample. From the genomic sequence of V. vadensis, one gene was found to encode agarase; however, its enzymatic properties have never been characterized. The gene encoding the putative agarase (NCBI reference number ZP_01923925) was cloned by PCR and expressed in E. coli Rosetta-gami by using the inducible $T_7$ promoter of pET28a(+). The expressed protein with a $6{ imes}His$ tag at the N-terminus was named $His_6$-VadG925 and purified as a soluble protein by $Ni^{2+}$-NTA agarose affinity column chromatography. The purification of the enzyme was 26.8-fold, with a yield of 73.2% and a specific activity of 1.02 U/mg of protein. The purified $His_6$-VadG925 produced a single band with an approximate MW of 155 kDa, which is consistent with the calculated value (154,660 Da) including the $6{ imes}His$ tag. Although VadG925 and many of its homologs were annotated as agarases, it did not hydrolyze agarose. Instead, purified $His_6$-VadG925 hydrolyzed an artificial chromogenic substrate, p-nitrophenyl-${eta}$-D-galactopyranoside, but not p-nitrophenyl-${alpha}$-D-galactopyranoside. The optimum pH and temperature for this ${eta}$-galactosidase activity were pH 7.0 and $40^{circ}C$, respectively. The $K_m$ and $V_{max}$ of $His_6$-VadG925 towards p-nitrophenyl-${eta}$-D-galactopyranoside were 1.69 mg/ml (0.0056 M) and 30.3 U/mg, respectively. $His_6$-VadG925 efficiently hydrolyzed lactose into glucose and galactose, which was demonstrated by TLC and mass spectroscopy. These results clearly demonstrated that VadG925 is a novel ${eta}$-galactosidase that can hydrolyze lactose, which is unusual because of its low homology to validated ${eta}$-galactosidases.