A work machine with a boom that can be derricked, includes: a first derricking angle detector that detects a derricking angle of the boom at a base end of the boom; a second derricking angle detector that detects a derricking angle of the boom at a front end of the boom; a first flexible volume acquisition part that acquires a flexible volume of the boom based on a detected angle by the first derricking angle detector and a detected angle by the second derricking angle detector; a second flexible volume acquisition part that acquires a flexible volume of the boom based on the detected angle by the first derricking angle detector; and a switching part that switches between acquisition of the flexible volume of the boom by the first flexible volume acquisition part and acquisition of the flexible volume of the boom by the second flexible volume acquisition part.