An adenovirus for use in a method of treating cancer, said vector containing a DNA construct for expression of Reduced Expression in Immobilized Cells/Dickkopf-3 (REIC/Dkk-3) DNA, which is prepared by functionally ligating the following (i) to (iv) to each other in this order, from the 5' terminal side: (i) a cytomegalovirus promoter; (ii) a REIC/Dkk-3 DNA selected from the following: (a) a DNA consisting of the nucleotide sequence shown in SEQ ID NO: 1, (b) a DNA having at least 85% sequence identity with the sequence shown in SEQ ID NO: 1, hybridizing under stringent conditions to a DNA consisting of a nucleotide sequence complementary to the nucleotide sequence shown in SEQ ID NO: 1 and encoding a protein having cancer cell death-inducing activity and/or tumor cell growth-suppressing activity, (c) a polynucleotide consisting of a nucleotide sequence ranging from the 1 st nucleotide to any single nucleotide from the 117 th nucleotide to the 234 th nucleotide in the nucleotide sequence shown in SEQ ID NO: 1 and encoding a protein having cancer cell death-inducing activity and/or tumor cell growth-suppressing activity, or (d) a polynucleotide having at least 85% sequence identity with the sequence shown in SEQ ID NO: 1, hybridizing under stringent conditions to a polynucleotide consisting of a nucleotide sequence complementary to a nucleotide sequence ranging from the 1 st nucleotide to any single nucleotide from the 117th nucleotide to the 234th nucleotide in the nucleotide sequence shown in SEQ ID NO: 1, and encoding a polypeptide having cancer cell death-inducing activity and/or tumor cell growth suppressing activity; (iii) a polyA sequence; and (iv) enhancers prepared by linking a human Telomerase Reverse Transcriptase (hTERT) enhancer, an SV40 enhancer, and a CMV enhancer in this order. (i) a cytomegalovirus promoter; (ii) a REIC/Dkk-3 DNA selected from the following: (a) a DNA consisting of the nucleotide sequence shown in SEQ ID NO: 1, (b) a DNA having at least 85% sequence identity with the sequence shown in SEQ ID NO: 1, hybridizing under stringent conditions to a DNA consisting of a nucleotide sequence complementary to the nucleotide sequence shown in SEQ ID NO: 1 and encoding a protein having cancer cell death-inducing activity and/or tumor cell growth-suppressing activity, (c) a polynucleotide consisting of a nucleotide sequence ranging from the 1 st nucleotide to any single nucleotide from the 117 th nucleotide to the 234 th nucleotide in the nucleotide sequence shown in SEQ ID NO: 1 and encoding a protein having cancer cell death-inducing activity and/or tumor cell growth-suppressing activity, or (d) a polynucleotide having at least 85% sequence identity with the sequence shown in SEQ ID NO: 1, hybridizing under stringent conditions to a polynucleotide consisting of a nucleotide sequence complementary to a nucleotide sequence ranging from the 1 st nucleotide to any single nucleotide from the 117th nucleotide to the 234th nucleotide in the nucleotide sequence shown in SEQ ID NO: 1, and encoding a polypeptide having cancer cell death-inducing activity and/or tumor cell growth suppressing activity; (a) a DNA consisting of the nucleotide sequence shown in SEQ ID NO: 1, (b) a DNA having at least 85% sequence identity with the sequence shown in SEQ ID NO: 1, hybridizing under stringent conditions to a DNA consisting of a nucleotide sequence complementary to the nucleotide sequence shown in SEQ ID NO: 1 and encoding a protein having cancer cell death-inducing activity and/or tumor cell growth-suppressing activity, (c) a polynucleotide consisting of a nucleotide sequence ranging from the 1 st nucleotide to any single nucleotide from the 117 th nucleotide to the 234 th nucleotide in the nucleotide sequence shown in SEQ ID NO: 1 and encoding a protein having cancer cell death-inducing activity and/or tumor cell growth-suppressing activity, or (d) a polynucleotide having at least 85% sequence identity with the sequence shown in SEQ ID NO: 1, hybridizing under stringent conditions to a polynucleotide consisting of a nucleotide sequence complementary to a nucleotide sequence ranging from the 1 st nucleotide to any single nucleotide from the 117th nucleotide to the 234th nucleotide in the nucleotide sequence shown in SEQ ID NO: 1, and encoding a polypeptide having cancer cell death-inducing activity and/or tumor cell growth suppressing activity; (iii) a polyA sequence; and (iv) enhancers prepared by linking a human Telomerase Reverse Transcriptase (hTERT) enhancer, an SV40 enhancer, and a CMV enhancer in this order.