A hydraulic device includes a housing and a solenoid valve to be mounted to the housing. The solenoid valve includes a plunger and a plunger-mounting sleeve in which the plunger is mounted. The plunger-mounting sleeve includes a sleeve member and a sleeve flange having a flange portion and a cylindrical portion provided at the radially outer edge of the flange portion. The plunger-mounting sleeve is fixed to the housing by seating a flange portion of the sleeve flange on a shoulder formed on a mounting hole formed in the housing, press-fitting a mounting ring loosely fitted around the sleeve member into the cylindrical portion of the sleeve flange, thereby pressing the flange portion against a seating surface of the shoulder, and further wedging the cylindrical portion into the inner periphery of the mounting hole.