Visitors to Guinea-Bissau must obtain a visa on arrival (available to all nationalities and also online in a form of pre-enrolment or at one of the Guinea-Bissau diplomatic missions) unless they come from one of the countries or territories that are visa exempt.
Visa exemption
Citizens of the following 14 countries and territories can visit Guinea-Bissau without a visa:
Holders of diplomatic or service passports issued to nationals of Angola, Mozambique and Sao Tome and Principe do not require a visa.
Holders of passports issued by all countries can obtain a visa on arrival for a maximum stay of 90 days.
References
Visa policy of Guinea-Bissau Wikipedia(Text) CC BY-SA