A mobile crane comprising: a lower traveling body which includes a pair of crawlers each extending in forward and rearward directions and spaced apart from each other in leftward and rightward directions; an upper slewing body supported on the lower traveling body slewably about a slewing axis; a tiltable attachment (14, 17, 21, 22) including a boom tiltably supported on the upper slewing body; and a physical quantity detector, wherein the lower traveling body has a reaction force receiving part for receiving a reaction force from the ground at a position away from the slewing axis in a boom direction in a state where the pair of crawlers is in contact with the ground, the boom direction coinciding with a horizontal component of a direction in which the boom extends from the upper slewing body, the physical quantity detector is configured to detect a physical quantity which changes in accordance with a change in the reaction force received from the ground by the reaction force receiving part, the boom direction corresponds to one of the forward and rearward directions of the lower traveling body, and each of the pair of crawlers includes: a crawler frame extending in the forward and rearward directions; and a first wheel supported on one of a front end and a rear end of the crawler frame and rotatable about a rotational axis, the one end being away from the slewing axis in the boom direction, characterized in that the first wheel serves as the reaction force receiving part. a lower traveling body which includes a pair of crawlers each extending in forward and rearward directions and spaced apart from each other in leftward and rightward directions; an upper slewing body supported on the lower traveling body slewably about a slewing axis; a tiltable attachment (14, 17, 21, 22) including a boom tiltably supported on the upper slewing body; and a physical quantity detector, wherein the lower traveling body has a reaction force receiving part for receiving a reaction force from the ground at a position away from the slewing axis in a boom direction in a state where the pair of crawlers is in contact with the ground, the boom direction coinciding with a horizontal component of a direction in which the boom extends from the upper slewing body, the physical quantity detector is configured to detect a physical quantity which changes in accordance with a change in the reaction force received from the ground by the reaction force receiving part, the boom direction corresponds to one of the forward and rearward directions of the lower traveling body, and each of the pair of crawlers includes: a crawler frame extending in the forward and rearward directions; and a first wheel supported on one of a front end and a rear end of the crawler frame and rotatable about a rotational axis, the one end being away from the slewing axis in the boom direction, characterized in that a crawler frame extending in the forward and rearward directions; and a first wheel supported on one of a front end and a rear end of the crawler frame and rotatable about a rotational axis, the one end being away from the slewing axis in the boom direction, characterized in that the first wheel serves as the reaction force receiving part.