A breather device for an engine, comprising: a valve holder; and a breather valve supported by the valve holder, wherein the valve holder includes: a holder body having a valve port of the breather valve; an outlet passage pipe formed of metal and having a blow-by gas outlet passage formed inside, the blow-by gas outlet passage communicating with the valve port and being located below the valve port; and a heater that heats the outlet passage pipe, an outer peripheral surface of the outlet passage pipe is wrapped with the holder body formed of a material having lower thermal conductivity than that of the outlet passage pipe, the holder body has a heater insertion port, and the heater is inserted from the heater insertion port toward a heat input wall of the outlet passage pipe, wherein the outlet passage pipe includes: a pipe start end wall closing a pipe start end; a communication port provided in the pipe upper wall near the pipe start end and communicating with the valve port; and a pipe terminal peripheral wall having a pipe outlet opened at the opposite end of the pipe start end wall, and the pipe start end wall is the heat input wall of the outlet passage pipe, characterised in that the holder body has a downward hole that connects the valve port and the communication port located below the valve port, the communication port is formed downward in series with the downward hole, the blow-by gas outlet passage faces in a front-back direction substantially perpendicular to a direction of the communication port below the communication port, when a back side is defined to be one side in the front-back direction, the heat input wall is disposed at a back end of the blow-by gas outlet passage, and the heater is inserted toward the heat input wall from the back side. a valve holder; and a breather valve supported by the valve holder, wherein the valve holder includes: a holder body having a valve port of the breather valve; an outlet passage pipe formed of metal and having a blow-by gas outlet passage formed inside, the blow-by gas outlet passage communicating with the valve port and being located below the valve port; and a heater that heats the outlet passage pipe, an outer peripheral surface of the outlet passage pipe is wrapped with the holder body formed of a material having lower thermal conductivity than that of the outlet passage pipe, the holder body has a heater insertion port, and the heater is inserted from the heater insertion port toward a heat input wall of the outlet passage pipe, wherein the outlet passage pipe includes: a pipe start end wall closing a pipe start end; a communication port provided in the pipe upper wall near the pipe start end and communicating with the valve port; and a pipe terminal peripheral wall having a pipe outlet opened at the opposite end of the pipe start end wall, and the pipe start end wall is the heat input wall of the outlet passage pipe, characterised in that the holder body has a downward hole that connects the valve port and the communication port located below the valve port, the communication port is formed downward in series with the downward hole, the blow-by gas outlet passage faces in a front-back direction substantially perpendicular to a direction of the communication port below the communication port, when a back side is defined to be one side in the front-back direction, the heat input wall is disposed at a back end of the blow-by gas outlet passage, and the heater is inserted toward the heat input wall from the back side.