A medical-electrode hydrogel having a laminate structure of layer A and layer B, wherein layer A comprises a monomer-derived component, water, a humectant, a water-insoluble polymer having tackiness and an amphiphilic polymer, the water is comprised in a proportion of 13 to 40 wt% based on the total amount of layer A the water-insoluble polymer is comprised in a proportion of 3 to 20 wt% based on a total amount of layer A, the amphiphilic polymer is a polyvinyl alcohol having a saponification degree of 50 to 75% and is comprised in a proportion of 0.05 to 5 wt% based on the total amount of layer A; layer B comprises a monomer-derived component, water and a humectant and is substantially free of a water-insoluble polymer having tackiness and a polyvinyl alcohol; an amount of the water based on a total amount of layer B is the amount of water based on the total amount of layer A ± 10 wt%; an amount of the humectant based on the total amount of layer B is an amount of the humectant based on the total amount of layer A ± 10 wt%; the monomer-derived component is a cross-linked water-soluble polymer; and the humectant is a polyhydric alcohol. layer A comprises a monomer-derived component, water, a humectant, a water-insoluble polymer having tackiness and an amphiphilic polymer, the water is comprised in a proportion of 13 to 40 wt% based on the total amount of layer A the water-insoluble polymer is comprised in a proportion of 3 to 20 wt% based on a total amount of layer A, the amphiphilic polymer is a polyvinyl alcohol having a saponification degree of 50 to 75% and is comprised in a proportion of 0.05 to 5 wt% based on the total amount of layer A; comprises a monomer-derived component, water, a humectant, a water-insoluble polymer having tackiness and an amphiphilic polymer, the water is comprised in a proportion of 13 to 40 wt% based on the total amount of layer A the water-insoluble polymer is comprised in a proportion of 3 to 20 wt% based on a total amount of layer A, the amphiphilic polymer is a polyvinyl alcohol having a saponification degree of 50 to 75% and is comprised in a proportion of 0.05 to 5 wt% based on the total amount of layer A; layer B comprises a monomer-derived component, water and a humectant and is substantially free of a water-insoluble polymer having tackiness and a polyvinyl alcohol; an amount of the water based on a total amount of layer B is the amount of water based on the total amount of layer A ± 10 wt%; an amount of the humectant based on the total amount of layer B is an amount of the humectant based on the total amount of layer A ± 10 wt%; the monomer-derived component is a cross-linked water-soluble polymer; and the humectant is a polyhydric alcohol. comprises a monomer-derived component, water and a humectant and is substantially free of a water-insoluble polymer having tackiness and a polyvinyl alcohol; an amount of the water based on a total amount of layer B is the amount of water based on the total amount of layer A ± 10 wt%; an amount of the humectant based on the total amount of layer B is an amount of the humectant based on the total amount of layer A ± 10 wt%; the monomer-derived component is a cross-linked water-soluble polymer; and the humectant is a polyhydric alcohol.