A strain detector includes a strain-causing portion, an insulation film formed on the strain-causing portion, a strain gauge formed on the insulation film and configured to detect the strain generated by the strain-causing portion as electric signals, an electrode connected to the strain gauge, a bonding pad extending from the electrode, a bonding wire connected to the bonding pad, and an insulative resin layer covering the strain gauge without covering the bonding pad and the bonding wire.