To provide a cutting blade mounting structure and a strip cutting device capable of attaching a cutting blade to a shaft at low cost and reducing work burden.

An upper side arbor shaft 44 to which an upper blade 22 is attached is fixed to a housing 40 through an insulation member 58. When a precision feed screw 66 is rotated from a condition in which the upper blade 22 is separated from a lower blade 24 and the contact of the upper blade 22 with the lower blade 24 is known by lighting of a lamp, the precision feed screw 66 is further rotated in a predetermined direction by a predetermined amount to perform alignment of a position of the upper blade 22. Since the insulation member 58 does not affect mounting position precision of the upper blade 22, machining with high precision is not necessary. Since it is unnecessary to remove the insulation member 58 when dismounting and replacing the upper blade 22, management for preventing breakage of the insulation member 58 becomes unnecessary.