A photomultiplier tube comprising: a housing which includes a first substrate and a second substrate which are arranged so as to oppose each other, with the respective opposing surfaces (40a, 20a) made with an insulating material; an electron multiplying part which has a plurality of stages of dynodes (33a - 33l) arrayed so as to be spaced away sequentially along one direction from a first end side to a second end side on the opposing surface of the first substrate; a photocathode which is installed on the first end side inside the housing so as to be spaced away from the electron multiplying part, thereby converting incident light from outside to photoelectrons to emit the photoelectrons; and an anode part which is installed on the second end side inside the housing so as to be spaced away from the electron multiplying part to take out electrons multiplied by the electron multiplying part as a signal; wherein a power supplying part for supplying power to the electron multiplying part is installed on the opposing surface of the second substrate, the electron multiplying part is provided with supporting bases (52a - 52l), each of which is electrically connected to the end part of each of the plurality of stages of dynodes (33a - 33l) on the side of the first substrate and installed so as to be astride electron multiplying channels formed with the plurality of stages of dynodes (33a - 33l) and a power supplying member (53a - 53l) which is formed so as to extend from one end part of both end parts of each of the supporting bases (52a - 52l) in a direction along the opposing surface of the first substrate to the second substrate and electrically connected to the power supplying part, the supporting bases (52a - 52l) are constituted in such a manner that the both end parts are joined to the opposing surface, and also a central part held between the both end parts is spaced away from the opposing surface, and wherein a recessed part is formed on the opposing surface of the first substrate and the central part of the supporting bases (52a - 52l) is arranged over the recessed part, thereby being spaced away from the opposing surface, characterized, in that the recessed part is formed so as to be astride a plurality of supporting bases (52a - 52l) individually connected to the plurality of stages of dynodes (33a - 33l), and a cross sectional area (S 1) along the opposing surface (20a, 40a) at the one end part of the both end parts on the side of the power supplying member (53a - 53l) is made greater than a cross sectional area (S 2) at another end part of the both end parts. a housing which includes a first substrate and a second substrate which are arranged so as to oppose each other, with the respective opposing surfaces (40a, 20a) made with an insulating material; an electron multiplying part which has a plurality of stages of dynodes (33a - 33l) arrayed so as to be spaced away sequentially along one direction from a first end side to a second end side on the opposing surface of the first substrate; a photocathode which is installed on the first end side inside the housing so as to be spaced away from the electron multiplying part, thereby converting incident light from outside to photoelectrons to emit the photoelectrons; and an anode part which is installed on the second end side inside the housing so as to be spaced away from the electron multiplying part to take out electrons multiplied by the electron multiplying part as a signal; wherein a power supplying part for supplying power to the electron multiplying part is installed on the opposing surface of the second substrate, the electron multiplying part is provided with supporting bases (52a - 52l), each of which is electrically connected to the end part of each of the plurality of stages of dynodes (33a - 33l) on the side of the first substrate and installed so as to be astride electron multiplying channels formed with the plurality of stages of dynodes (33a - 33l) and a power supplying member (53a - 53l) which is formed so as to extend from one end part of both end parts of each of the supporting bases (52a - 52l) in a direction along the opposing surface of the first substrate to the second substrate and electrically connected to the power supplying part, the supporting bases (52a - 52l) are constituted in such a manner that the both end parts are joined to the opposing surface, and also a central part held between the both end parts is spaced away from the opposing surface, and wherein a recessed part is formed on the opposing surface of the first substrate and the central part of the supporting bases (52a - 52l) is arranged over the recessed part, thereby being spaced away from the opposing surface, characterized, in that the recessed part is formed so as to be astride a plurality of supporting bases (52a - 52l) individually connected to the plurality of stages of dynodes (33a - 33l), and a cross sectional area (S 1) along the opposing surface (20a, 40a) at the one end part of the both end parts on the side of the power supplying member (53a - 53l) is made greater than a cross sectional area (S 2) at another end part of the both end parts.