A battery pack including a plurality of battery cells arranged in a row in a first direction, the plurality of battery cells being arranged obliquely with respect to the first direction; a first holder plate and a second holder plate arranged to face each other and support the plurality of battery cells therebetween, the first holder plate including a plurality of first steps repeatedly arranged to surround and support first vertically protruding edges of the plurality of battery cells and the second holder plate including a plurality of second steps repeatedly arranged to surround and support second vertically protruding edges of the plurality of battery cells; and at least one cooling channel in the first steps.