A blow-by gas device of a supercharger-equipped engine, the blow-by gas device including a supercharger in a portion downstream of a throttle valve in an intake passage, the blow-by gas device comprising: a PCV valve; and a blow-by gas passage connected to a portion of the intake passage located between the throttle valve and the supercharger and to an engine body, the blow-by gas passage introducing blow-by gas discharged from the engine body into the intake passage via the PCV valve, wherein the supercharger includes a supercharger body including therein a rotor chamber, a rotation shaft (81, 82) rotatably supported on at least one bearing part (83, 84) communicating with the rotor chamber, the rotation shaft (81, 82) being rotatable by power of a driving source, and a supercharger rotor (341, 342) provided integrally with the rotation shaft (81, 82) and rotatably disposed inside the rotor chamber, the supercharger body includes a space portion (34f, 34h) communicating with the bearing part (83, 84), the space portion (34f, 34h) is connected to a communication passage (73, 73', 74), and the communication passage (73, 73', 74) guides the blow-by gas discharged from the engine body to the space portion (34f, 34h), characterized in that the supercharger body includes an intake-side space portion communicating with the bearing part on an intake side and a discharge-side space portion communicating with the bearing part on a discharge side, the intake-side space portion is connected to a first communication passage communicating with a portion upstream of the PCV valve in the blow-by gas passage or with the engine body, and the discharge-side space portion is connected to a second communication passage branching off from a portion downstream of the PCV valve in the blow-by gas passage. a PCV valve; and a blow-by gas passage connected to a portion of the intake passage located between the throttle valve and the supercharger and to an engine body, the blow-by gas passage introducing blow-by gas discharged from the engine body into the intake passage via the PCV valve, wherein the supercharger includes a supercharger body including therein a rotor chamber, a rotation shaft (81, 82) rotatably supported on at least one bearing part (83, 84) communicating with the rotor chamber, the rotation shaft (81, 82) being rotatable by power of a driving source, and a supercharger rotor (341, 342) provided integrally with the rotation shaft (81, 82) and rotatably disposed inside the rotor chamber, the supercharger body includes a space portion (34f, 34h) communicating with the bearing part (83, 84), the space portion (34f, 34h) is connected to a communication passage (73, 73', 74), and the communication passage (73, 73', 74) guides the blow-by gas discharged from the engine body to the space portion (34f, 34h), characterized in that the supercharger body includes an intake-side space portion communicating with the bearing part on an intake side and a discharge-side space portion communicating with the bearing part on a discharge side, the intake-side space portion is connected to a first communication passage communicating with a portion upstream of the PCV valve in the blow-by gas passage or with the engine body, and the discharge-side space portion is connected to a second communication passage branching off from a portion downstream of the PCV valve in the blow-by gas passage.