A mobile computer includes: an operation casing 2 including a right side face 2g, a top surface 2a, and a back surface 2d; a lid component 4 configured to cover a battery insertion/detachment opening 6a formed in the right side face 2g; and an engaged component 5 formed on the top surface 2a. The lid component 4 includes: a securing portion 4e secured to a part of the operation casing 2; a lid portion 4a configured to cover the battery insertion/detachment opening 6a; an engaging portion 4d having an engagement hole 4f that engages with the engaged component 5; a first bent portion 4c configured to connect between the securing portion 4e and the lid portion 4a; and a second bent portion 4b configured to connect between the lid portion 4a and the engaging portion 4d, so as to be integrated into the lid component 4.