Reservoir tank and brake hydraulic pressure generator

A reservoir tank comprising:

• an upper case;
• a lower case positioned below the upper case and coupled to the upper case;
• a partition wall extending from the upper case toward the lower case and separating, in a horizontal direction, a first room and a second room which are included in a space inside the upper case and the lower case coupled to each other;
• and
• a partition member having a first wall covering the first room from below, and a second wall protruding upward from the first wall and being in contact with the partition wall, wherein
• the partition wall is provided with a first slit which opens to a lower edge of the partition wall and which establishes communication between the first room and the second room, and
• at least an edge of the first slit and the second wall form a first hole which establishes communication between the first room and the second room and which is positioned above the first wall.