A mobile radiation generator comprising: a carriage part that includes wheels; a pillar that is provided on the carriage part; an arm part where an irradiation section is mounted on a free end and a base end is rotatably supported by the pillar, the position of the irradiation section in a vertical direction being changed in a case in which the arm part is rotated while the base end serves as a base point; a spring that generates negative rotational moment in a negative direction where the irradiation section is displaced upward against positive rotational moment that acts on the arm part in a positive direction due to own weight of the arm part and the irradiation section in a case in which a direction where the irradiation section is displaced downward in the vertical direction is prescribed as the positive direction; and a friction mechanism that generates a frictional force acting in a direction opposite to a direction where the arm part is to be rotated due to a difference between the positive rotational moment and the negative rotational moment and cancelling a difference between the positive rotational moment and the negative rotational moment in a case in which the magnitude of the positive rotational moment and the magnitude of the negative rotational moment are different from each other, characterized in that the pillar further comprises a frame member having a pair of frame plates that are disposed at intervals in a width direction and a mounting part comprising side plates (41A, 41B) that are disposed at an interval in the width direction such that they are received in the interval between the two frame plates of frame member and the friction mechanism includes on both sides of each side plate (41A, 41B) one set of friction plates (46, 47) that includes a first friction plate rotated with the rotation of the arm part and a second friction plate disposed so as to face the first friction plate to be rotated and not rotated regardless of the rotation of the arm part and generates a frictional force by contact between friction surfaces of the respective friction plates (46, 47), and a normal force generating section that includes a biasing unit applying a biasing force in a direction where the friction surfaces of the set of friction plates (46, 47) are pressed against each other and generates a normal force on the friction surfaces. a carriage part that includes wheels; a pillar that is provided on the carriage part; an arm part where an irradiation section is mounted on a free end and a base end is rotatably supported by the pillar, the position of the irradiation section in a vertical direction being changed in a case in which the arm part is rotated while the base end serves as a base point; a spring that generates negative rotational moment in a negative direction where the irradiation section is displaced upward against positive rotational moment that acts on the arm part in a positive direction due to own weight of the arm part and the irradiation section in a case in which a direction where the irradiation section is displaced downward in the vertical direction is prescribed as the positive direction; and a friction mechanism that generates a frictional force acting in a direction opposite to a direction where the arm part is to be rotated due to a difference between the positive rotational moment and the negative rotational moment and cancelling a difference between the positive rotational moment and the negative rotational moment in a case in which the magnitude of the positive rotational moment and the magnitude of the negative rotational moment are different from each other, characterized in that the pillar further comprises a frame member having a pair of frame plates that are disposed at intervals in a width direction and a mounting part comprising side plates (41A, 41B) that are disposed at an interval in the width direction such that they are received in the interval between the two frame plates of frame member and the friction mechanism includes on both sides of each side plate (41A, 41B) one set of friction plates (46, 47) that includes a first friction plate rotated with the rotation of the arm part and a second friction plate disposed so as to face the first friction plate to be rotated and not rotated regardless of the rotation of the arm part and generates a frictional force by contact between friction surfaces of the respective friction plates (46, 47), and a normal force generating section that includes a biasing unit applying a biasing force in a direction where the friction surfaces of the set of friction plates (46, 47) are pressed against each other and generates a normal force on the friction surfaces.