A photomultiplier tube 1 is an electron tube comprising an envelope 5 including a frame 3b having at least one end part formed with an opening and an upper substrate 2 airtightly joined to the opening, and a photocathode 6 contained within the envelope 5, the photocathode 6 emitting a photoelectron into the envelope 5 in response to light incident thereon from the outside; wherein multilayer metal films 10b, 10a each constituted by a metal film made of titanium, a metal film made of platinum, and a metal film made of gold laminated in this order are formed at the opening and the joint part between the upper substrate 2 and opening; and wherein the frame 3b and upper side substrate 2 are joined to each other by holding a joint layer 14 containing indium between the respective multilayer metal films 10b, 10a.