A vehicle brake device is provided with a master cylinder, a master piston slidably arranged in the master cylinder, an input piston slidably arranged in the master cylinder to be separated from the master piston and defining a separation chamber, an input piston moving amount detecting section for detecting the moving amount of the input piston, a master piston moving amount calculating section for calculating the moving amount of the master piston based on the moving amount of the input piston, and a contact inferring section for inferring the contact of the input piston with the master piston based on the moving amount of the input piston and the moving amount of the master piston.