A safety device for a construction machine, comprising: a gate lock detection section that detects an operation position of a gate lock lever that is manipulated to a lock position in which instructions from operating levers of the construction machine are disabled and a lock release position in which instructions from the operating levers are enabled; a tilting detection section that detects tilting status of the construction machine; a seat belt detection section that detects whether an operator is wearing a seat belt of the construction machine; and a control section that controls a warning section so that a warning is given to the operator on the basis of information detected by the gate lock detection section, the tilting detection section, and the seat belt detection section, wherein the warning section includes a seat belt warning lamp that shows whether the operator is wearing the seat belt and a sound notification section that outputs a warning sound, such that the control section is configured to: when the seat belt detection section detects that the operator is wearing the seat belt, make the warning section release the warning; when the seat belt detection section detects that the operator is not wearing the seat belt and the gate lock detection section detects that the gate lock lever is manipulated to the lock position, control the warning section so as to turn on the seat belt warning lamp as a first warning; when the seat belt detection section detects that the operator is not wearing the seat belt, the gate lock detection section detects that the gate lock lever is not manipulated to the lock position, and the tilting detection section does not detect the tilting status of the construction machine, control the warning section so as to flicker the seat belt warning lamp as a second warning of which attention arousing performance is higher than that of the first warning, when the seat belt detection section detects that the operator is not wearing the seat belt, the gate lock detection section detects that the gate lock lever is not manipulated to the lock position, and the tilting detection section detects the tilting status of the construction machine, control the warning section so as to flicker the seat belt warning lamp and output the warning sound as a third warning of which attention arousing performance is higher than that of the second warning, and when giving the third warning, control the warning section so as to increase sound volume of the warning sound as tilting detected by the tilting detection section becomes larger. a gate lock detection section that detects an operation position of a gate lock lever that is manipulated to a lock position in which instructions from operating levers of the construction machine are disabled and a lock release position in which instructions from the operating levers are enabled; a tilting detection section that detects tilting status of the construction machine; a seat belt detection section that detects whether an operator is wearing a seat belt of the construction machine; and a control section that controls a warning section so that a warning is given to the operator on the basis of information detected by the gate lock detection section, the tilting detection section, and the seat belt detection section, wherein the warning section includes a seat belt warning lamp that shows whether the operator is wearing the seat belt and a sound notification section that outputs a warning sound, such that the control section is configured to: when the seat belt detection section detects that the operator is wearing the seat belt, make the warning section release the warning; when the seat belt detection section detects that the operator is wearing the seat belt, make the warning section release the warning; when the seat belt detection section detects that the operator is not wearing the seat belt and the gate lock detection section detects that the gate lock lever is manipulated to the lock position, control the warning section so as to turn on the seat belt warning lamp as a first warning; when the seat belt detection section detects that the operator is not wearing the seat belt, the gate lock detection section detects that the gate lock lever is not manipulated to the lock position, and the tilting detection section does not detect the tilting status of the construction machine, control the warning section so as to flicker the seat belt warning lamp as a second warning of which attention arousing performance is higher than that of the first warning, when the seat belt detection section detects that the operator is not wearing the seat belt, the gate lock detection section detects that the gate lock lever is not manipulated to the lock position, and the tilting detection section detects the tilting status of the construction machine, control the warning section so as to flicker the seat belt warning lamp and output the warning sound as a third warning of which attention arousing performance is higher than that of the second warning, and when giving the third warning, control the warning section so as to increase sound volume of the warning sound as tilting detected by the tilting detection section becomes larger.