A battery, which can inhibit raise of an internal resistance even when temperature change or mechanical shock is applied, and which has superior productivity is provided. A safety mechanism and a battery cover are installed at an open part of a battery case by caulking through a gasket. Inside of the battery case is sealed. A flange part of the battery cover contacts with a flange part of a safety valve of the safety mechanism. A surface roughness of the contact face is set to be in the range from about 0.5 .mu.m to about 5.5 .mu.m based on an arithmetic average roughness Ra. A contact resistance between the battery cover and the safety valve is thereby reduced. Further, a maximum height Ry of the contact face is preferably in the range from about 8.0 .mu.m to about 50.0 .mu.M.